There's a lot of FUD in there (maybe a conflict of interest?). The media industry operates fine on an ad-based model. Yes, reports of disappearing reviews have only been anecdotal and never close to proven (and obviously unnecessary). People love to review things and there are tons of ways to incent such. It should be possible to manage fraudulent reviews as many other companies do (Google included)(Max and Jeremy also have a lot of experience there). The extortion thing is simply ridiculous. Yelp was originally much more "social grafty" and has stepped back significantly from that. I have little doubt it will continue to find ways to maximize review relevance aside from social graph.
Not sure what you mean by the media industry working fine on an ad-based model. If you mean it makes money then possibly it does, but if you mean that it typically manages to remain a trustworthy independent source of news/reviews etc, then I'd strongly suggest that it fails quite badly.
Advertisers threatening to pull their accounts because the publication/channel has done something they don't like is the most visible manifestation of this, but the modern newspaper industry is basically run at the behest of advertisers and the typical output of these papers (just look at the amount of PR-driven stories that make it into the average paper on a daily basis) largely reflects this.
