Don't get me wrong, I agree with you completely that the entire situation is completely ridiculous. Unfortunately, in the States here, every cellular carrier that I know of has fine print in their terms of use agreement that you sign with your contract which can be summed up as, "We can cancel your service or any part of your service for any reason or no reason at all!"
So the first step is raising a red flag by extreme data usage, AT&T then looks at what you're doing, notices your usage patterns aren't that of a smartphone, then they cancel your data plan. If you're lucky they'll notify you that they've dropped your data plan, if you're unlucky you'll have a $600 bill from checking your email a few times.
I think you'd be hard pressed to find a single person who thinks that the way the cellular carriers in the US work are ethical, fair to the consumer, or anything like that.
Unfortunately, we don't have much choice. AT&T, Verizon, and Sprint all have the buying power to just absorb any competition that offer better rates. Alltel was getting spry with the cellular market offering plans that were a little too good drawing customers away from the big 3. Not a problem, 28 billion dollars later they're now a part of Verizon!
It will probably stay this way until there is some kind of open WiMax network and VoiP phones that operate on WiMax for pennies on the dollar compared to cellular. Or, in other words, not for a very long time.