I'm not 100% sure Google Voice is a valid example for this theory but here goes: By accepting applications that compete with the iPhone's core capabilities they stand to lose way more revenue than they do by angering some nerds by banning the application in the first place.

Here's a question. Does Apple really need tech geeks for the iPhone to be successful anymore? It's already a mainstream success, the large majority of users are probably not tech oriented at this point and the hardcore types (whom, I'm sorry, represent a small market share) are already more interested in Android phones because they like the "hacker" feel of it's operating system.