- I'm not in USA.
- My friends are really reluctant to start using new services. It took ages for them to start using Facebook.
- My friends probably do not have Google accounts. In fact they would probably be more likely to use this if this was a Facebook app.
- As you say everyone needs to eat, so it is safe to assume that each of my friends will have dinner anyway. So if I want to have dinner with a particular friend, can't I just SMS them? I think they would find this more natural than me trying to talk them into signing up for something.