How can you tell if someone is a freeloader when they start downloading? You can't right now.

Personally I would simply like a few extra http headers, and without those a download will not occur.

eg:

Hosts: 8/10
Leafs: 0
Shared-Files: 1440302342/435

Shared-Files is usually the only thing one might wnat to check.. the rest would just be nice for ultrapeer **** :P This would then tell a host whether or not somebody is a freeloader. If all clients keep this _right_, then one can simply reply when one is considered a freeloader:

HTTP <error> Freeloaders aren't allowed to download

or whatever... Thoughts?