First Question: Initially it would decrease my efforts on the iPhone. But once it's in place, and my summer job is over, I think I will have time to support 2 platforms.

Second question: Yes and No. In particular for Android I don't think the growth path would be different. If I were to expand I would probably expand into facebook right now. The reason being that an umbrella category like facebook will also include a subset of iPhone users. Supporting a big category like facebook apps will indirectly help the other channel as well.

Those are the answers to your questions... and I generally agree with your core answer. I guess my only issue is that one of my biggest advantages as a small company is my ability to be nimble and it seems like I am throwing this advantage away. That being said I'm not sure how much that argument stands up to the argument of "get significant traction in one area before expanding".