http://articles.latimes.com/2009/feb/11/business/fi-lazarus1...
I read it when JWZ pointed to it from his "I Hate Yelp" post:
http://jwz.livejournal.com/1002269.html
JWZ runs the DNA Lounge in San Francisco, and is "pretty sure" that he was in fact given a pay-to-play pitch for Yelp placement and review management.
For some very specific kinds of businesses --- the kinds unlikely to attract a constant stream of casual reviews --- Yelp has been useful to me. For restaurants and bars, it's less than worthless; "reviewers" clearly do make up random stories ("Publican serves O-Reida fries! Violet Hour serves well-liquor!").
In Chicago, we have LTH Forum. It is the polar opposite of Yelp. It is a PHPBB named after a specific Chicago Chinese restaurant that has completely owned up all the reputable food reviews in Chicago. It has no salespeople, makes no profit, is aggressively NOT SEO'd (LTH is never going to be the first hit for anything), appears to be layed out in PHPBB's default template, and is better than any other source of reviews in any city in the US. Every year it gives out awards (the LTH "Great Neighborhood Restaurants"), which --- again, this is a PHPBB site --- are hung in the windows of every restaurant that has received them.
You could never post a half-assed troll review on LTH and get anywhere with it. 15 people who'd been there and talked with the chef would write counter-reviews, and the moderator would probably strike your post. Someone needs to figure out how to scale this model.