Arrington reported that Yelp earned $30 million in revenue this year and it is expected to jump to $50 in 2010. Yelp is a very popular local search site. It is arguably the best of its kind.
If Google buys them, you would have to think they would fold it into their Google Maps and Local services. They did that with FeedBurner and so many other brands they bought (i.e GrandCentral, etc). At the same, YouTube was bought by Google and because of its popularity, Google never moved it to Google Video.
I wonder how Google would handle Yelp. It would be a shame to see the Yelp brand go away.