A lot of social software and Web 2.0 applications are based on an idea of commons and contribution without expecting anything back in a measured or formal sense. Think of the 1 percent rule. However, indirectly everyone benefits... at least that's the theory.
But now in the peer-to-peer (P2P) space we have BitTyrant:
"BitTyrant is designed to make efficient use of your scarce upload bandwidth, rewarding those users whose upload allocations are fair and only allocating excess capacity to other users."
The academics and students at the University of Washington that developed BitTyrant say that this isn't as "selfish" as it sounds:
"A big difference between BitTyrant and existing BitTorrent clients is that BitTyrant can detect when additional upload contribution is unlikely to improve performance. If a client were truly selfish, it might opt to withhold excess capacity, reducing performance for other users that would have received it. However, our current BitTyrant implementation always contributes excess capacity, even when it might not improve performance. Our goal is to improve performance, not minimize upload contribution."
This actually sounds similar to how the old dial-up Bulletin Boards used to work, except the upload to download ratios were typically a lot softer. However, at the end of the day this is really more about sharing of a limited resource (bandwidth) than ensuring people share content. So unfortunately, if this does impact on the way P2P works its more likely to impact on those where bandwidth is a premium.
UPDATE: Care of Brady Forrest on the O'Reilly Radar blog, the Monkey Bites blog at Wired magazine provides futher commentary on BitTyrant and other anti-social P2P software. Don't forget to read the comments too.