...in Nevada:
http://www.dailytech.com/ATT+Experiments+with+Bandwidth+Caps/article13355.htm
Following TWC's lead, AT&T is rolling out a trial that caps downloads to either 20GB/month or 150GB/month depending on your plan. The initial trial is only in Nevada. TWC started a similar trial with caps of only 5GB/month and 40GB/month depending upon the plan in Texas earlier this year. Comcast has also implemented similar limits. I hate to see this as it seems like a huge step backwards in service and IMO it's just a way to raise new revenue. Personally, that 150GB cap that AT&T is trialing would probably suite me fine right now, but as more and more HD content becomes available via the internet I can see a time in the near future where that 150GB limit will seem antiquated. Being a TWC internet customer, implementing a 40GB limit would force me to switch to AT&T because while I don't hit it every month, I do hit that 40GB limit on occasion.

With Netflix rolling out HD
With Netflix rolling out HD streaming on Xbox 360 this month and via their Roku box by year's end, bandwidth caps are going to be problematic. They need to invest in infrastructure rather than capping bandwidth.