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

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

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.

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