The ironic part about the 2 gb per month cap is that it will have absolutely no impact on their network.
It will convince people to pay more for what they have, and will keep them from abandoning their other services like a broadband card or DSL line.
My reasoning is simple. They will only pass a certain amount of data at a time to each user. If too many users are wanting data, then all of them get slightly lower throughput BUT the exact same total amount of data. When the network is loaded it takes 10 seconds to download that picture instead of 7. Unless they have designed the network really bad, the whole picture will still get there even when it's very badly overloaded.
So the total bytes is a red herring designed to let them charge more. If the wanted to cut back on usage they should do what DSL does, and charge by the speed that they will deliver it. You'd have a 56KBPS, 750KBPS... 4MBPS service. But then they could not brag about having the fastest network.
Oh, on topic: I listen to an hour of streaming Sirrus or AOL radio each business day while walking. Less than 1GB a month.
Daniel
P.S. You know they are lying about too much network usage when they disable tethering but will sell you a broadband PC card that does the same thing using the same cellular channels and network... for $59 a month.