My concern is simply that trying to be the de-facto app means you'll never really get the traction you need to become successful. I hate to invoke Facebook here

My concern is simply that trying to be the de-facto app means you'll never really get the traction you need to become successful. I hate to invoke Facebook here, but even they started with a very limited market. Once there was enough demand, people were coming to them asking for access and they evolved. I like what you're saying about keeping it narrow by the communities you're targetting. If it's truly useful, and generic, then people will start finding their own alternative uses. I wouldn't have three different type of question on your front-page header; 1. Lost my Dog, if you spot it ... 2. Wanna play a game? 3. What is... I'd pick one type (personally, the 2nd) and stick to that. 1. is only useful with significant localised usage and 3. is better left to something like twitter for now. Whatever you do, best of luck.