Yea it's actually somewhat ironic. I'm sure companies would like to keep congestion down and hoping people don't download like crazy at the same time. But now you get the scenario [and this includes ADSL 3GB cap] where people WILL make sure they use their entire -paid for- bundle/amount.
So i wonder if this doesn't cause alot of slowdowns at the end of the month? [and it will only get worse the more people sign up]. It'll be impossible to actually regulate the usage, people will be 'saving' bandwidth somewhere in the month and then 'overuse' another time in the month and it will happen all the same general periods for everyone.
Current system actually forces you 'not to waste money' by wasting bandwidth on the network
My guess is this:
Week 1 : High Usage [everyone who did finish off their bundle will now be downloading whatever they couldn't download previous month]
Week 2 : Low Usage [saving]
Week 3 : Low Usage [saving]
Week 4 : Extremely High Usage [Those that did not finish off bundles will now be downloading any crap they can find in order to do so + the regular end of the month things [banking,bills etc etc] ]
So in the end networks are digging a hole for themselves, they will not be able to smooth out usage and you will have a situation where 2 weeks of the month you can barely use the network and the other 2 weeks it's clean but then you're busy saving up bandwidth.