Well, I can speak to this, since I just recently upgraded my computer and needed to copy my iTunes songs from one system to the other. On my old computer, I deauthorized the old computer, then on the new computer I authorized the new computer, copied the files, and shazam it worked!
THere is a first time for everything. Personally, I won't let any of that crap on my PC. It's my data not theirs.
An interesting thing about purchasing through MusicMatch, I can only make three copies of a song or cd. Now I haven't lost a cd yet, but I can see where that could become a pain.
In any case, I've simply stopped purchasing music, in any format- it's not worth it and I don't need it. (I can conceive of a parallel to cigarette addiction and music addiction- in a strictly limited sense.)