If you think about it, it's pretty much the same thing as twitter, except the social graph is built more implicitly. In exchange for a larger selection of relevant content, you have to sift through more noise. But it probably feels better to vote if you know your vote counts differently for some users. You're no longer just one number in a statistic, but part of a much more complicated ranking system. Best of all, your votes significantly affect your own experience on the website.
A dynamic social graph like that would probably obviate the need for even categorizing content, let alone "jumping ship" when the community decays.
There are some drawbacks though. If you implemented it in reddit/hacker news, there would no longer be a "front page of x" to serve as a symbolic milestone for your submission. Without context, "2000 upvotes" has ambiguous importance. Also, a different ranking system exists for each cluster in your social graph, which sounds like a fun engineering problem.
A dynamic social graph like that would probably obviate the need for even categorizing content, let alone "jumping ship" when the community decays.
There are some drawbacks though. If you implemented it in reddit/hacker news, there would no longer be a "front page of x" to serve as a symbolic milestone for your submission. Without context, "2000 upvotes" has ambiguous importance. Also, a different ranking system exists for each cluster in your social graph, which sounds like a fun engineering problem.