said by dgass:
Charging users for data usage above the bandwidth they sell with the speed of your connection each month is nothing more than a double bill. Billing you twice for the same thing.
If they greatly reduce the existing charge, then it's not billing twice for the same thing. For example if they charge $10 or $20 per month to have a connection, and then they charge $x for y gigabytes, that's two separate line items for two separate things.
I think elitefx has a point -- lots of people are subscribing to services that offer far more than they need, and as a result are likely paying more than they need to.
It's not a perfect comparison, but take newsgroups access for instance. Many people think paying $10/mo for unlimited is the only way to go, and that's because they download a LOT of content so for them it probably is the best way to go. But I hardly download anything at all, so why pay $10/mo when the same amount will buy me a block that will last 2 years?
If people had the same options when choosing how to buy their internet, I think more than you expect would choose the block method.