I'm not a mobile developer, but if I were, that wouldn't bother me. The concept of an app store shipping on every iPhone and Apple doing the marketing for you... it's pretty enticing and IMHO well worth that 30%. I'd imagine a high-profile application (read: fad) would gather more money, traffic, and downloads on a forced-down-your-throught app store on the iPhone than on Android where your users have to go more or less out of their way to get it.