Check out this article on Inc.com:
You've Been Yelped
We’ve always been impressed with how Yelp elegantly serves-up not just user reviews but community, geo-targeting and local search. If you’ve not seen their iPhone app, it’s outstanding.
How has Yelp affected your small business? As the article mentions, some business owners can obsess about it... but the obsessed might feel better after reading our previous post, "Bad" reviews can be surprisingly good.

Yep, I know people in the food industry who definitely obsess over it. There's some controversy about Yelp's business tactics, too - some people have accused them of penalizing business owners who don't pay for their premium services.
San Francisco Photographer
Posted by: Bay Area web design | March 03, 2010 at 11:39 AM