If Apple is OK with it, what's the problem?
OK, obviously it's screwing over their customers. But, if Apple wants their application to work this way, then they aren't being harmed by AT&T.
I wonder, is the blocking happening at the tower or on the phone?
Probably phone level (client/server for FaceTime).
I would actually expect that AT&T is smarter than this and is doing an App level and/or protocol level block. Eg. iPhone + plan = x means no 3g at the device level. If this is at a network level, then they'd have a lot of work. In theory, this would block FaceTime only on iOS devices such as iPhone/iPad.
Apple doesn't really care, and has left these decisions to the carrier (I think an attempt at changing the overall App model into a 'service' model) which is what AT&T wants anyway (App tolls).
Why I have a concern on this - is that this allows carriers to filter apps that they feel they 'own', and can charge fees on.
This is/was Ed Whitacre's argument all along. Google is gonna pay ATT if they want ATT's internet customer's to have the ability to connect to them.
Since it didn't work on the wireline side, they are playing it out on the wireless side in a more gentle and poitically correct level!