How about allowing apps that block calls in the app store from third-parties?
A year and a half ago I passed on buying a new iPhone, even though I owned a 3GS and out of frustration I've gone out of my way to buy a Galaxy S. The Android Marketplace (as it was called back then) had several apps for blocking calls, some of them broken on my Galaxy S, but I could find one that worked and solved my problem.
So you know, I'm sure that one day Apple will wake up and provide the very best experience for blocking phone calls and SMS messages. But that's something I've been doing for at least 1 year and a half already, which goes to show just how fucked up is Apple's gatekeeper culture. "So this expensive gadget doesn't solve your real problems, but look how user-friendly it is".