Ah-pook has considered the filter problem and will suggest the function(s) thereof.

1) Filtering files that are not copyrighted, or have been okayed for sharing, angers the composers who would like to share their music. These composers then post their grievances on this and other forums. These posts are available to napster management who will use them to support their arguments in court that filtering was never a viable option, and would hamper their ability to run a legitimate business. That is, this is simple damage control. If you began to realize that you were in danger of being sliced translucently thin and fried crispy in court, you'd be afraid too, and would use any means at your disposal to avoid that fate.
2) Napster had a percentage goal of file reduction which it quickly reached. Thanks to the genius types of this realm, whom ah-pook is virtually begging to enter the afterdeath, a vast profusion of altered song titles and artist names were invented. This has forced napster to filter material at a Draconian level to eliminate altered titles of copyrighted materials. Napster will continue to increase filtration until no demonstrable copyrighted material is available on their site. Only after they have achieved this NEW goal will any of their resources be dedicated to restoring legitimately sharable files. And probably not then either. They will, after all, be very busy simultaneously starting up their 'pay peer file' service and dodging legal bullets in the courtroom.
3) ah-pook will now mete out some good old fashioned entertaining cwej annoying frontier justice afterdeath punishments for the offendees:

Picture the head of the Orb-is-one. Ah-pook's assistants have enlarged it to the size of Jupiter. Encircling this ghastly globe is a planetary ring, much like Saturn's. It's irridescent, almost cd like, strangely beautiful. Let's zoom into the inner edge of the disc, nearest planet Roy. We can now see that the ring is composed of trillions of small Orb-is-ones. From the inner edge of the disc a steady stream of Orb-is-ones falls slowly away towards the hideous pasty ground far below. A terrible keening falsetto emanates from each as they accelerate until they begin to smoke, leaving fiery trails of ash behind them.

Lets follow one down, shall we?

Smoking meteoRoy has pretty much lost all his 'trademark' feaures by the time we are able to discern some sort of activity in one of the many craters below. Mired in stinking yellow goo a desperate troop of copyright file name changers frantically dodge incoming meteoRoys, badly impeded by the blistering hot, charred, crooning Orb-is-onites who litter the scarscape. Yeah, and they are "Crying", all right.

And it's NEVER "over".