On Phex you can BAN hosts, but most of these hosts don't know that they download (and share) fake-files!
I think it would be better to BAN (SHA1 code of) fake-files, see this image (i was searching for 'thisfileisveryfakeohyeah':
Just search for ANY name, even names that don't excist... you will see alot of fake-files, and even more hosts.
You can BAN hosts, but the fake-files will still appear in your search-results from other hosts... you can BAN fake-files (SHA1 code) and then these files will not appear anymore in your search-results, no matter how many hosts are sharing these fake-files!
Banning fake-files will be more efficient then banning hosts if you ask me... but i'm not an expert so maybe i'm completely wrong...