No bit rate does suggest fakes. I normally filter out wm files myself. And most files under 2 MB I give the junk tag to.
To filter out certain extensions ... go to Tools > Options > Filters > Keywords. For example, add .wm
Oh and on the idea of filtering, see some pointers here How to find music & also Direct instructions to eliminate porn from results

(There are some gnutella clients who share audio files that for some reason sometimes don't show bit rate .... I can't remember which clients .. shareaza or morpheus, etc.)

It might be worth adding this to your LW: Hostiles List so it helps filter out known spam ip's. This list needs to be kept up to date btw so renew it occasionally. See if it helps or not.

Thanks for the pointers - had found & used the "hostiles" list - now subs to thread to make sure of updates.

One other thing that these files seem to have in common is the "Browse Host" button is always greyed out as well - Is this just an indication that users have just deliberately not enabled sharing in Options/Sharing ?
Or would these users files not actually show up in a search? (Guess that makes more sense!)

Hope this makes some kinda sense - Haven't developed a LW variety of OCD about these files, just interested to learn more about the possibilities.