The devil is in the details. I think a lot of devs realize they need a very polished app and substantial viral value - the trouble is that you can't just will either of those things into existence, or even buy them.

Executing a good app is really hard, and people who can do it consistently are very rare still. Getting a really cohesive, well-built app done is more than just hiring the most expensive ObjC coders and designers you know.