The only other scenario it could be would be due to not acknowleding a copyright infringement claim. Although the "Six Strikes" program is considered dead, most ISPs still obey the spirit of that program in order to maintain their safe harbor status as an Internet Provider.
Six Strikes generally had an outline where the first few notices required acknowledgement. Subsequent notices would result in "Education" courses, or punishments such as being throttled to 128kbps for a month, and finally, disconnection.
And yes, the throttling aspect is real. Had a friend end up with throttled FiOS for a month because his roommate torrented something while my friend was on vacation. Needless to say... roommate isn't allowed to use that connection anymore :-).
