It isn't a port-blocking device that Road Runner is using, or actually it doesn't have to be.

There is a device made by Packeteer called the Packetshaper and it can read into the packets at layer 3 through layer 7 and determine what app you are running across your connection regardless of port. They can put the ISP class of this device in line and tell it to either limit or completely block p2p and any other app for that matter that they want.

Or they can assure guarantee a certain amount of their bandwidth to the applications they want and leave the rest to be shared by all other apps.

It can also be done by user or subnet. You could block Instant messaging for your employees subnet but allow the executive subnet to use it all they want.

Many businesses are starting to place these in because they can block p2p, winmedia, and streaming stuff on a per user basis. Or the more relaxed office settings will assign a very low priority to p2p etc...so when any other app comes along, it overpowers the p2p.

--

Connorsdad