Part of the genius of the reward system here is that it is "training" people to see the direct benefit of helping others. I sit here, and by upvoting your comment, I can literally see that 7c (no fortune, by any means) went into your virtual tip jar. The point is that the system teaches us that it feels good to help others... and so we create content, and others help US by leaving these "tips."
Which is a helluva lot better than the eternal dog-eat-dog world of take-take-take out there.
The fact that there is as much of a sense of "community" here as there is, is brilliant too. There are lots of palces with user generated content... but nowhere else have I seen this level of engagement. We actually address each others... not just a thumbs up or a *nice post, bro."