On a couple of the packages, it's possible to blow through your entire monthly cap in 6 hours - and I've seen people do it.
Data caps will rise substantially over the next five years. By 2020x, they'll be commonly at several hundred gigabytes at 5G speeds across the US and Europe, with unlimited data at lower speeds as a universal feature. No doubt numerous carriers will offer variations of unlimited data.
"One of the new AT&T plans will cost $25 per month and offer two gigabytes of data per month, which AT&T says will be enough for 98 percent of its smart phone customers. Additional gigabytes will cost $10 each."
This is in 2010.
Today that $25 will actually get you HALF the data it did in 2010, five years ago.
I'm waiting for the day they just take it away.