Take a look at http://steemit.com/ for instance. It's kind of a Reddit clone based on that model. I think it still only has fewer than 1 million users, which means the quality of the user-generated posts won't be as good even as that from the (much larger) Reddit right now. But the tipping itself seems to be (largely) working.
I say largely, because last I checked months ago, I still thought it prioritized a sort of feedback loop for the "rich to get richer" on the platform. But this is easy to change with an algorithm update. My guess is the main reason they don't do it is because having people earn "$1,000 per post" is getting them a lot of publicity and word of mouth promotion, compared to if they made it so "almost everyone can earn at least $1-$5 on every post".
But as the platform grows (and the money on the platform grows with it) I would like to imagine they won't allow the "famous posters" to make tens of thousands of dollars on every post, and they will try to redistribute that to the rest of the platform users. If they don't do that, the platform will fail under its own weight anyway, and another competing cryptocurrency tipping platform will take its place.
But overall, I think this sort of platform has extremely high potential. I've seen many smaller-time Youtubers start using it, because it almost immediately allowed them to make more money than they made from YouTube alone.
Oh, and perhaps the "secret sauce" of the Steemit.com site is that it also spreads the earnings with the upvoters/downvoters as well as the commenters, which is basically paying for the curation of the platform, thus offering real monetary incentive to do those actions properly (although I imagine there may be some who try to abuse it, too).