I think sites that run some kind of an automatic ranking or otherwise a user-driven voting system are better protected from spam. To make it even better there s

I think sites that run some kind of an automatic ranking or otherwise a user-driven voting system are better protected from spam. To make it even better there should the second level with weighted users (user ranking in other words) to compensate massive automatic registrations of fake users. I'm sure it is much easier for Flickr, for instance, to fight spam than for Cragislist, because Flickr has an excellent automatic ranking system of photos based on users' (implicit) votes plus users' weights. This at least prevents spam from slipping into the daily top-500, and the rest is not that important. They host all kinds of garbage anyway and that doesn't bother the community. This is what makes spammers turn away from Flickr, I think. I have never seen any spam on Flickr's top-500 page (well, except those crappy images with anything-Apple insanely upvoted by a bunch of Apple fans).