said by KrK:
The thing is about throttling is that while it makes better sense in terms of managing traffic, it doesn't mean extra profits from overages. Therefore caps and overages will be the model, because ISP's can then make extra money when people go over rather then just slowing their bandwidth usage.
Except most ISPs dont charge for overages they just cut you off. Which is actually LOST revenue since you no longer have a paying customer.