:) Well, there are rules, (official and unofficial) guidelines and "best practices". The first two, you can't break them, but you can break the third and still be in the App Store. I think an annoying direct channel falls in the third category. I've seen many apps/games do it. Two of them (of top of my head) are blockbusters and have sold tens of millions of copies combined: Doodle Jump & Jetpack Joyride. So, yes, you can do it and still be in the App Store.