Interesting take on social networking
How will you prevent abuse?
How will you make money? Buy the app? Pay for catchy hashtags?
Hashtags probably won't be unique, how do you control who gets what? What happens if user A and user B both use #soccer for their neighborhood game, but they aren't in the same neighborhood?
Must people use your app to subscribe? If not, how will you grow your userbase? If so, why would people bother?