·Time Warner Cable
This could be the result of Time Warner not capping their service. These two companies seem to do things in lockstep (see Beaumont metered billing trials). I suspect that when TWC's Britt announced that Time Warner would continue offering unlimited plans to customers who want it, AT&T put this on the back-burner.
...so they're laying off U-Verse caps for marketing reasons.
Either that, or AT&T is just incompetent, and they haven't been able to due this due to technical snags.
AT&T U-Hearse - RIP Unlimited Internet 1995-2011