Sure, I love user  generated content, but can it ever pay the bills? I don’t think so. At least not  in Yelp’s case. Here’s why:
Yelp caters to the  wrong person. If you’re after advertising dollars, it’s not part-time, unpaid  writers that you should cater to–it’s small business owners! And small business  owners HATE free-for-all commenting on their wares or services. I worked a lot  with restaurant owners while running WestChesterMenu.com and know they really  want to put a hurt on the Yelpers of the world. Sure, they could police all the  social sites and try to counter each negative remark–but anyone who knows small business owners  knows they don’t have a extra minute in their day to cater to non-core  activities. 
Can there be a balance? 
Maybe. But there would have to be two different sites–probably owned by two different  companies. For example, there should be one site that provides factual info  (name, address, phone, hours, pics, menu, directions, ‘official review’…) and  one for reviews from the masses… and they could link to each other. Perhaps Google  and Yelp can do that if they make up. What do you think?
It’s also crossed my mind that Yelp should focus more. Perhaps they should just be working on restaurants or just hair dressers or mechanics. Isn’t it easier to own expertise in a specific market rather than every market? Or, perhaps they can make Yelp channels… maybe hire some coaches to get folks to write more constructively… Just some ideas Yelp… in case you’re listening.