"[R]estaurants find that they themselves no longer own the customer relationship."
This is the dumbest thing I've read today. I am sitting in your restaurant! I am voting with my dollars by choosing to show up at your establishment! If I like what you have to offer, odds are I'll be happy to give up some personal information.If you want to know my email address to inform me of special events, or to give me a gift certificate for my birthday, then just ask me! It's not that hard.
Additionally, if I need a reservation to eat at your establishment, and you're not on Urbanspoon's Rez system or on OpenTable, you may as well not even exist. I'm not going to call you and a dozen other places looking for a last minute table. It's simply not worth my time.