I briefly considered building it over an afternoon, but I'm not sure it would really work on the Internet.
My gut feeling is that within a few days it would be full of spam and inane comments, because there's absolutely no sense of having a shared responsibility for a physical place in your neighbourhood. It's also unlikely to build the same sense of community from people stopping at the same time and talking to each other.
Tired of giving the same advice over and over again. Don't make me open my e-mail just to give you feedback about your site. You have a webpage! Create a form and receive feedback right from it!
Other than that, looks promising. Some aesthetic changes would do good, but looks nice. Consider OpenID or OAuth, to gain traction from social networks.
