Google is reportedly in closing negotiations to buy Yelp, the local business review site founded in 2004 by two PayPal veterans. An acquisition price has not been disclosed, but sources close to the deal said it is more than $500 million.

Some sources have expressed uncertainty as to why Google would purchase Yelp since it already provides search and review systems within Google Maps, but Yelp has more (and broader) local data. The search giant could undoubtedly benefit by melding Yelp's content and audience with its own Web products, all the way down to its Google Maps Navigation Android app.

Yelp will supposedly post around $30 million in revenue for 2009, with estimates as high as $50 million for 2010. The business had a $200 million valuation during its last round of venture capital funding in early 2008, but its worth has probably increased since.