There certainly are a lot of digg clones nowadays. I wonder if it will be like search where everyone thinks it's a crowded market for a solved problem and then someone with an actually intelligent algorithm comes along and mops up.
I think it's more than an algorithm problem: initially with a site like that, it's all about getting more people, because without them, the site is worth nothing. Then, all of a sudden, poof, you succeed, but you get a bunch of flaming morons, and the quality goes down the tubes. Maybe you're in a position to make some money, but I wouldn't consider something like reddit or digg an unqualified 'success' in terms of making the world a better place.
