One thing I was wondering about the iTunes match is if they don't have some of your music, will they ask if you want to upload it to the cloud? I recall Steve saying years ago the intention was to have every piece of music ever written up on the store, and it would be a nice touch if Apple offered to pirate your music that they didn't have.
Yes you can upload the stuff they don't have, apple have said this already.
Not really classed as pirating though... Lol