Comparison of Unwanted Software Installed by P2P Programs

Endleman's done a great job compiling a list and comparison of P2P, right down to the licensing info.

http://www.benedelman.org/spyware/p2p/

The links to other projects on the top right of the page have some interesting information as well. Especially

WhenU Violates Own Privacy Policy

http://www.benedelman.org/spyware/whenu-privacy/

I'd rather just stick to bittorrent and use tools like Sharezaa and torrentspy.com