I've been pleased to see that YouTube Content ID usually just results in attribution (a good thing!) and monetisation (ads) - it's not totally illegal to upload someone else's song.

There are a couple of times when it has been totally deleted though (Universal Studios Japan deleting Monoeyes songs), so that's why I prefer not to use my personal Google account for sharing content - losing access to GMail as a result of sharing something on YouTube is not a risk I'd like to take.

I wish there were a way to bulk-upload music (from, say, the 1.3 TB MySpace Dragon Hoard), but personal accounts are limited to 50 songs per day.