This is what they get for trying to mix advertising with user generated content. There are too many conflicts of interest between Yelp, advertisers, and anonymous users. Who would buy an ad for a page that can be easily defaced? No one who isn't promised censorship. It's a shame because Yelp is a great service. Maybe they could become more like a search engine, with links direct to vendor sites and user reviews in a separate section on Yelp. Then ads could go direct to business sites, eliminating the bad review issues.