Simpler idea: Paid search engine that ranks sites based on how often the users click results from that site (and didn't bounce, of course). The fact that it's

Simpler idea: Paid search engine that ranks sites based on how often the users click results from that site (and didn't bounce, of course). The fact that it's paid prevents sybil attacks (or, at least, turns a sybil attack into a roundabout way of buying ads). Of course, at this point, you are now the product even though you paid. But it's a tactic that worked for WoW for ages.