Google bought Zagat. It gets a long-standing trusted name in the ratings biz to enhance Google Maps and Places.
Expect Yelp to be kind of upset about this because it's had a series of grumbles with Google over how content gets listed in search results. So if you're searching on a Thai restaurant, Google would sometimes display its own customer reviews even though Yelp's site is arguably more popular for that specific function. Now, Google will have Zagat information, which it seems likely to give preferential treatment as well.
Zagat has historically been a subscriber based service where you pay for the info. Google isn't saying they'll do away with that on the Zagat site but I would be pretty surprised if they didn't knock down the pay wall to better spread the content and monetize it with ads.