Some WISPs do, some small indies might. Verizon, IIRC, is planning to do this if they get too many copyright infringement complaints about a user (the so-called "six strikes" policy). -- Developer: Tomato/MLPPP, Linux/MLPPP, etc »fixppp.org
The six strikes thing is entirely an AUP-defined construction (there's no legal basis for introducing it), and any ISP in Canada who wants to could likely implement it just the same. -- Developer: Tomato/MLPPP, Linux/MLPPP, etc »fixppp.org
the biggest one is probably explorenet and their FAP policy. but it's not a feeling thing, it's a formula based process. I'm sure others due it, and i'm pretty sure others have been caught throttling certain protocols before.