Zagat, the restaurant review site has just been acquired by Google (NASDAQ: GOOG) for an undisclosed amount.

Google plans to integrate Zagat with Google Maps and offer it as part of their local offerings which includes Google Places. I guess Google also plans to tied this into Google Offers as part of their social play after Google’s failed bid to acquire Groupon.

“Moving forward, Zagat will be a cornerstone of our local offering—delighting people with their impressive array of reviews, ratings and insights, while enabling people everywhere to find extraordinary (and ordinary) experiences around the corner and around the world”, blogged Marissa Mayer, VP of Local, Google.

“With Zagat, we gain a world-class team that has more experience in consumer based-surveys, recommendations and reviews than anyone else in the industry. Founded by Tim and Nina Zagat more than 32 years ago, Zagat has established a trusted and well-loved brand the world over, operating in 13 categories and more than 100 cities. The Zagats have demonstrated their ability to innovate and to do so with tremendous insight. Their surveys may be one of the earliest forms of UGC (user-generated content)—gathering restaurant recommendations from friends, computing and distributing ratings before the Internet as we know it today even existed. Their iconic pocket-sized guides with paragraphs summarizing and “snippeting” sentiment were “mobile” before “mobile” involved electronics. Today, Zagat provides people with a democratized, authentic and comprehensive view of where to eat, drink, stay, shop and play worldwide based on millions of reviews and ratings.”

This is being viewed as a major negative for Yelp, OpenTable (NASDAQ: OPEN), which is now down almost 9% on the news and UrbanSpoon, which is owned by IAC Interactive (NASDAQ: IACI).

Zagat recently struck a deal with UrbanSpoon, a competitor of OpenTable and Yelp to provide content for the site.

This acquisition puts Google in the content creation business. Now besides being a search engine Google is also leading you to its own content like Google Place, Google Offers and Zagat.