Interestingly, in Australia we have had Data Caps for a significant amount of time (2002 I believe was when Telstra introduced the 3gb Cable Cap).
I know it's not US based, but looking at ISP's and their offerings elsewhere, there are options available. For example I have an Unlimited ADSL2+ connection from TPG (www.tpg.com.au). The trend locally seems to be ISP's offering more data and more value for money (Unlimited in some cases, but 500GB / 1TB plans for marginal fees per month)
I'm also with TPG and can't fathom having a cap, much less the typically tiny ones offered. Recently I noticed that Optus is now offering an unlimited account for a reasonable price. I've heard anecdotally from people working there that it would be cheaper for Optus to do away with the caps because of the internal overhead that tracking and accounting requires.
I know it's not US based, but looking at ISP's and their offerings elsewhere, there are options available. For example I have an Unlimited ADSL2+ connection from TPG (www.tpg.com.au). The trend locally seems to be ISP's offering more data and more value for money (Unlimited in some cases, but 500GB / 1TB plans for marginal fees per month)