It's one thing to borrow a CD, listen to it, and return it. Quite another to make a copy and listen to it in perpetuity, and especially to then distribute other copies to other people.
You're going to have people who claim that "theft (or whatever they'd prefer to call it) is theft" but let's be reasonable here. There's a big difference between going into a supermarket and stealing one candy bar versus going in and completely emptying the shelves. To equate the making of a mixtape for one friend with the placement of a file online where it will be accessible by potentially millions of people is silly.

