There were reports in September that AT&T throttles "unlimited data" customers when its networks are particularly congested, but apparently congestion actually has nothing to do with it when it comes to LTE.
AT&T's 3G and non-LTE (that means 4G HSPA+ to AT&T) subscribers are slowed down at the 3GB mark when the networks are busy, but LTE users are throttled after 5GB in a billing cycle regardless of network traffic.
That's better than the policy AT&T once held of simply throttling unlimited users' data automatically as a rule, but still. Come on.
Ars Technica spoke with one AT&T subscriber who noticed his speeds slowing and confirmed the policy with the carrier, and a customer service representative reportedly told him there's nothing they can do about it.
AT&T's own support site confirms that this is the case for users with "legacy unlimited data plans," and it's not uncommon among other carriers, either - the T-Mobile plan I signed up for in November has severe throttling after 3GB, but at least they were upfront about it.
Hopefully the federal government's efforts to take AT&T to task for its "deceptive and unfair" policies has some lasting effects on this industry, as things appear to be getting worse, not better.