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In Praise of Freeloaders

by Clay Shirky
12/01/2000

As the excitement over P2P grew during the past year, it seemed that decentralized architectures could do no wrong. Napster and its cousins managed to decentralize costs and control, creating applications of seemingly unstoppable power. And then researchers at Xerox brought us P2P's first crisis: freeloading.

Freeloading is the tendency of people to take resources without paying for them. In the case of P2P systems, this means consuming resources provided by other users without providing an equivalent amount of resources (if any) back to the system. The Xerox study of Gnutella (now available at FirstMonday) found that " ... a large proportion of the user population, upwards of 70 percent, enjoy the benefits of the system without contributing to its content," and labels the problem a "Tragedy of the Digital Commons."

The Tragedy of the Commons is an economic problem with a long pedigree. As Mojo Nation, a P2P system set up to combat freeloading, states in its FAQ:

Other file-sharing systems are plagued by "the tragedy of the commons," in which rational folks using a shared resource eat the resources to death. Most often, the "Tragedy of the Commons" refers to farmers and pasture, but technology journalists are writing about users who download and download but never contribute to the system.

To combat this problem, Mojo Nation proposes creating a market for computational resources -- disk space, bandwidth, CPU cycles. In its proposed system, if you provide computational resources to the system, you earn Mojo, a kind of digital currency. If you consume computational resources, you spend the Mojo you've earned. This system is designed to keep freeloaders from consuming more than they contribute to the system.

A very flawed premise

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Mojo Nation is still in beta, but it already faces two issues -- one fairly trivial, one quite serious. The trivial issue is that the system isn't working out as planned: Users are not flocking to the system in sufficient numbers to turn it into a self-sustaining marketplace.

The serious issue is that the system will never work for public file-sharing, not even in theory, because the problem of users eating resources to death does not pose a real threat to systems such as Napster, and the solution Mojo Nation proposes would destroy the very things that allow file-sharing systems like Napster to work.

The Xerox study on Gnutella makes broad claims about the relevance of its findings, even as Napster, which adds more users each day than the entire installed base of Gnutella, is growing without suffering from the study's predicted effects. Indeed, Napster's genius in building an architecture that understands the inevitability of freeloading and works within those constraints has led Dan Bricklin to christen Napster's effects "The Cornucopia of the Commons."

Systems that set out to right the imagined wrongs of freeloading are more marketing efforts than technological ones, in that they attempt to inflame our sense of injustice at the users who download and download but never contribute to the system. This plays well in the press, of course, garnering headlines like "A revolutionary file-sharing system could spell the end for dot-communism and Net leeches" or labeling P2P users "cyberparasites."

This sense of unfairness, however, obscures two key aspects of P2P file-sharing: the economics of digital resources, which are either replicable or replenishable; and the ways the selfish nature of user participation drives the system.

One from one equals two

Almost without fail, anyone addressing freeloading refers to the aforementioned "Tragedy of the Commons." This is an economic parable illustrating the threat to commonly held resources. Imagine that in an area of farmland, the entire pasture is owned by a group of farmers who graze their sheep there. In this situation, it is in the farmers' best interest to maintain herds of moderate size in order to keep the pasture from being overgrazed. However, it is in the best interest of each farmer to increase the size of his herd as much as possible, because the shared pasture is a free resource.

Even worse, although each herdsman will recognize that all of them should forgo increases in the size of their herd if they are acting for the good of the group, they also recognize that every other farmer also has the same incentives to increase the size of their herds as well. In this scenario, each individual has it in their individual interest to take as much of the common resources as they can, in part because they can benefit themselves and in part because if they don't someone else will, even though doing so produces a bad outcome for the group as a whole.

The Tragedy of the Commons is a simple, compelling illustration of what can happen to commonly owned resources. It is also almost completely inapplicable to the digital world.

Start with the nature of consumption. If your sheep takes a mouthful of grass from the common pasture, the grass exits the common pasture and enters the sheep, a net decrease in commonly accessible resources. If you take a copy of the Pink Floyd song "Sheep" from another Napster user, that song is not deleted from that user's hard drive. Furthermore, since your copy also exists within the Napster universe, this sort of consumption creates commonly accessible resources, rather than destroying them. The song is replicated; it is not consumed. Thus the Xerox thesis -- that a user replicating a file is consuming resources -- seems problematic when the original resource is left intact and a new copy is created.

Even if, in the worst scenario, you download the song and never make it available to any other Napster user, there is no net loss of available songs, so in any file-sharing system where even some small percentage of new users makes the files they download subsequently available, the system will grow in resources, which will in turn attract new users, which will in turn create new resources, whether the system has freeloaders or not. In fact, in the Napster architecture, it is the most replicated resources that suffer least from freeloading, because even with a large percentage of freeloaders, popular songs will tend to become more available.

Bandwidth over time is infinite

But what of bandwidth, the other resource consumed by file sharing? Here again, the idea of freeloading misconstrues digital economics. If you saturate a 1 Mb DSL line for 60 seconds while downloading a song, how much bandwidth do you have available in the 61st second? One meg, of course, just like every other second. Again, the Tragedy of the Commons is the wrong comparison, because the notion that freeloading users will somehow eat the available resources to death doesn't apply. Unlike grass, bandwidth can't be "used up," any more than CPU cycles or RAM can.

Like a digital horn of plenty, most of the resources that go into networking computers together are constantly replenished; "Bandwidth over time is infinite," as the Internet saying goes. By using all the available bandwidth in any given minute, you have not reduced future bandwidth, nor have you saved anything on the cost of that bandwidth when it's priced at a flat rate.

Bandwidth can't be conserved over time either. By not using all the available bandwidth in any given minute, you have not saved any bandwidth for the future, because bandwidth is an event, not a conservable resource. Unused bandwidth expires just like unused plane tickets do, and as long as the demand on bandwidth is distributed through the system -- something P2P systems excel at -- no single node suffers from the SlashDot effect, the tendency of sites to crash under massive load (named after the frequent crashes to small sites that crash after getting front-page placement on the news site SlashDot.org).

Given this quality of persistently replenished resources, we would expect users to dislike sharing resources they want to use at that moment, but indifferent to sharing resources they make no claim on, such as available CPU cycles or bandwidth when they are away from their desks. Conservation of resources, in other words, should be situational and keyed to user behavior, and it is in misreading user behavior where attempts to discourage freeloading really jump the rails.

Selfish choices, beneficial outcomes

Attempts to prevent freeloading are usually framed in terms of preventing users from behaving selfishly, but selfishness is a key lubricant in P2P systems. In fact, selfishness is what makes the resources used by P2P available in the first place.

Since the writings of Adam Smith, literature detailing the workings of free markets has put the selfishness -- or more accurately, the self-interest -- of the individual actor at the center of the system, and the situation with P2P networks is no different. Mojo Nation's central thesis about existing file-sharing systems is that some small number of users in those systems choose, through regard for their fellow man, to make available resources that a larger number of freeloaders then take unfair advantage of. This does not jibe with the experience of millions of present-day users.

Consider an ideal Napster user, with a 10 GB hard drive, a 1 Mb DSL line, and a computer connected to the Net round the clock. Did this user buy her hard drive in order to host MP3s for the community? Obviously not -- the size of the drive was selected solely out of self-interest. Does she store MP3s she feels will be of interest to her fellow Napster users. No, she stores only the music she wants to listen to, self-interest again. Bandwidth? Is she shelling out for fast DSL so other users can download files quickly from her? Again, no. Her check goes to the phone company every month so she can have fast download times.

Likewise, decisions she makes about leaving her computer on and connected are self-interested choices. Bandwidth is not metered, and the pennies it costs her to leave her computer on while she is away from her desk, whether to make a pot of coffee or get some sleep, is a small price to pay for not having to sit through a five-minute boot sequence on her return.

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