Anakim Border wrote:

First of all, do we really need *persistent* GUIDs? They won't help tracking malicious users, since anyone can always force his client to generate a new GUID when he likes.
 

I agree about your privacy concerns... I think a "good" client will offer the user a choice of both per session and global GUIDs.  If someone has queued files from you (and keeps your GUID as an identifer in their queue), a couple of hash matches (since you can request by hash, eliminating the pitfalls of you having reorganized your share in the meantime) should be enough for their client to learn your new GUID and re-establish you as a source for all those files.

- Todd