Yup, I hate that. I read that was incorporated into iTunes on behalf of the music/media companies.I stopped using iTunes the first time I switched computers and tried to sync my library. i may be dumb, i may have done it wrong, but it deleted everything that was on my itouch and put the stuff from the second computer only! That's not how I want things to be.
I buy that in 2001 when Apple needed them to get on board for the iPod. But not now, especially that the music companies allow Apple to sell DRM free music. The quickest way to turn people into pirates is to treat them like they're criminals.