They killed "shake the baby", they didn't kill iFart. You try figuring out where to draw the line. But there is no doubt that they are culling apps for their content; "weeding" so to speak.

With 3.3.1 Apple is trying to control the overal UX. They can't reject bad music from the iTunes Store, but they can enforce basic encoding standards, so the music doesn't sound like crap for reasons other than the artistic content.

When they removed the "sexy" apps they were using a rule that could be made specific and enforced consistently. The picked adult content because of the peculiar standards that humans (and especially Americans) have when it comes to sex.

Or maybe it's really difficult to phrase a definition for "college humor".

Don't forget that a hypothetical rejection of iFart would have to be backed by legalese from the TOS. What phrasing would you suggest they add? (Alternatively, quote the existing clause you would have them invoke.)