In Comcast’s new Terms of Service, the company explicitly admits that it degrades peer-to-peer traffic as a means of reducing their network load.
The company also admits that they will kick off end users who use (what they determine to be) too much bandwidth:
The Service is for personal and non-commercial residential use only. Therefore, Comcast reserves the right to suspend or terminate Service accounts where bandwidth consumption is not characteristic of a typical residential user of the Service as determined by the company in its sole discretion.
Harold Feld has a great explanation of why Comcast blocks p2p and boots the heaviest users: they don’t want to invest in the infrastructure to improve capacity, and they don’t want to use tiered pricing.
If only we could get network neutrality legislation…