Hmmm... I just downloaded Yelp to give it a try... It couldn't recognize my location so I had to point it to it on the map, but it doesn't know about the 2 restaurants within 500 m of where I live. I searched for Istanbul, where I'm going next week, and it didn't recognize the name. Then I made a search for restaurants in Paris and found 20. I guess the app must be useful to someone, but that's certainly not me.
Update: for Paris, Urban Spoon gives me a choice of three cities in the U.S. Double hmmm...