ISP should be very worried if they show they can control the type of packets being sent. Imagine if the mail carrier could be charged for the contents of a letter, or the telephone company had to be responsible for what people said on the phone!

Canadian ISP's should not engage in packet preferencing, or risk regulation http://www.michaelgeist.ca/resc/html...mar212005.html

European ISP's have to worry about taking on the job of enforcing copyright infringement.
http://constitutionalcode.blogspot.c...osals-isp.html

US ISP's have to worry about class-action suits LOTR posted a link about BearShare and a major ISP getting lawyers involved over this kind of interference.