While the app itself is fantastic, it's limited in scope and this functionality is already offered by Twitter, Facebook, or any other social network with status updates...still a good piece of software, but I can't see it catching on when you can do the same thing with just a simple Facebook or Twitter update where all your friends who are already in those social networks will see it...good follow-through, but the concept definitely needs work.
Thanks for the feedback. We're working on building out really interesting functionality while maintaining the simplicity of the app. We believe there is real value in providing a single forum where you can find what people in your network, and in your area are doing tonight.
Rather than hunting for plans posted on Twitter and/or Facebook, you can always rely on doingtonight to find out what people are doing tonight, without having to sort through all kinds of unrelated conversations.
We also think people have a different identity at night, and don't want to mix that up with their identity on the rest of the social graph.
But you're absolutely right that we have to do a lot of work before we realize this potential!