The business guys haven't yet figured out how generous to be with IAP currency. Everyone definitely wants to be generous with it, and Tiny Tower has proved it can work, but I'll admit, it's quite a risk.
Personally, I like to think that as long as we make a game that's actually fun, it won't matter too much how much free IAP currency there is.
Our next survival tower sim: Zombie Fortress
Zombie Fortress on TouchArcade