I use the 'sharing' services to try before I buy (and sometimes to find new artists). I don't mind paying for content, but I hate spending $18 for a cd w/ one good song.
The RIAA wants its cake and to eat it too. They want a perfectly docile public that will buy whatever tripe is pushed on them in large numbers.
That's what I like about Music Match. You can buy only the good songs.
I buy oldies and some new, fringe artists.