Union Square Cafe's maverick marketing

The other day I received a postcard in the mail from the Union Square Cafe in New York.
Not from owner Danny Meyer or chef Michael Romano, but from my friend, Megan, who had dined there a few days before. She later told me that the restaurant had provided free postcards--and postage--at the end of the meal, which struck me as a smart, inexpensive way for restaurants to get their name in front of potential customers.

So maybe I wasn't their ideal target market (it's been about seven years since I last ate at USC...though their ethereal gnocchi will never be forgotten), but for the price of a postcard, Meyer makes certain that a satisfied customer spreads the word--in a fun, personalized manner--to another potential diner before they've even left his restaurant. (Smart guy--no wonder he's been honored as the James Beard Foundation's "outstanding restaurateur.") It was the first time I've seen such a tactic, and I'm wondering if any local restaurants are doing or will do something similar.