As a side note, you can do something similar (albeit a thousand times safer, as you (= your computer) issues the certificates, not some unknown hacker) to fool Game Center.
I get maybe 20 Game Center invites from 8 year old kids on a daily basis... The reason is I faked my score on the popular game Jetpack Joyride (I'm #1 out of 16 million players), and also beat Minesweeper's hard map in a few milliseconds (second guy is I think over a minute)...
I did it just for fun and experiment, but apparently there are kids who really take Game Center seriously and I stopped doing it, not wanting to hurt their feelings. The instructions are here: http://corte.si/posts/code/mitmproxy/tute-gamecenter/index.h... , but please don't go crazy, and don't submit ridiculous scores like I did. You may get your account banned (which is not a great thing, if you're a developer).
This is really easy to do and a fun experiment to learn MITM attacks. My boss was gloating he was the best at jetpack joyride and the whole office had a good laugh knowing that I could always beat his best score by a small amount the day after het set it. Apparently that put a downer on his christmas because he spent so much time trying to beat me.
It did cross my mind whilst watching the traffic if you could spoof in app purchases but never took it any further.