That's a very loose definition of ads. Advertising typically implies that it's the restaurant promoting itself.

This is a reply to those below you, because I can't reply to them specifically.

Word of mouth is considered the best form of advertising you can get. Almost 100% of the time it's not even paid for.

I think being paid is pretty integral to the concept of an ad.

Well, don't forget, they bought Zagat. So even if it doesn't look like an ad, 'recommendations' are probably just another form.