According to Reuters, AT&T is currently working on implementing a fix for the iPhone upload data caps that many are experiencing in the US. According to the article, the problem affects less than 2% of the userbase, but the problem could take another 2-3 weeks to fix. Alcatel-Lucent, makers of the gear that powers the cell sites, started issuing a software patch today to fix the problem.
Apparently, the lack of service features such as tethering and MMS, one long a staple of other wireless carriers isn't AT&T's fault. Likewise, AT&T's inadequate bandwidth issues are also someone else's fault.