So, I wonder if this is the first salvo in a war on all the major carriers who use the same "unlimited but throttled" marketing scheme? If AT&T loses this one, will the FTC go after T-Mobile and Sprint, who also do this? (Verizon doesn't offer unlimited data to new customers, but had kept it going for grandfathered customers, and backed off from plans to throttle them[1]).
The issue doesn't seem to be the "unlimited by throttled" business model, but the adequate disclosure of that information to the consumer. Other carriers may have worded it differently. More importantly though, AT&T had a grandfathered contract with consumers for unlimited without throttling (or "true unlimited"). Those changes along with their vagueness make AT&T a special case. In any case though, I'm sure the other carriers will watch this case closely.
I am not a lawyer, but from reading the link, it sounds like the problem isn't that they throttled the data, but that they hid/lied about it.
Neither T-Mobile or Sprint hide the fact that they throttle / rate limit their subscribers for various reasons. So presumably, they are less at risk here.
As a former Sprint customer, I'll disagree about that particular carrier. Sprint has offered "unlimited" data for a long time, but after they finally got the iPhone a few years ago, they saw a surge in data usage and started implementing undisclosed and seemingly random soft caps on all their unlimited data customers, all while claiming they offered "truly unlimited data" that wasn't throttled. They have only very recently admitted[1] to throttling some of their customers, but it's actually been going on for a long time according to customer complaints in their support site.
As for T-Mobile, it's my understanding that they changed their policy to include the possibility of throttling and initially didn't disclose it until it was leaked[2].
Of course, neither of these situations are as customer-hostile as AT&T has been, so maybe the FTC won't go after them. But I wouldn't be surprised if Sprint and T-Mobile make changes to their policies if AT&T loses.
[1] http://www.cnet.com/news/verizon-backs-off-on-plans-to-throt...