Are they doing this? Is ANYONE doing this? Why are we 'solving' a problem before it's become a problem?
Let's stop beating around the bush here. What people really want here and why they support this crap is because they want their p2p file sharing to be as fast as possible.
In actuality, what will happen here is the same with all government regulations. Unintended consequences. This time, they will be diminished levels of service for everyone across the board and higher costs for that service.
Why the hell anyone would advocate for this claptrap is beyond me.
As far as I know it is true this is not based on them already having done it. This is based on the CEOs of some of these ISPs seriously talking about putting up toll booths on the Internet, degrading service unless the provider (VOIP, video, etc.) pays extra.
The other half of net neutrality is basically honesty in advertising, not quietly degrading the advertised service because a user has exceeded some unknown traffic cap. Put it all up front and charge for high traffic if necessary. They're doing this because they still want to be able to offer "unlimited" high-speed Internet, but not actually provide that service.