Music sites and porn sites seem to be the worst. I have everybody and his brother in here using my computer when I'm out, and before I put in all the spyware blockers I used to get a ton of stuff from Kazaa and other music downloading activities. I had to edit the Registry by hand, and sometimes it took a couple of days to get rid of it.
*Now* ya tell me!
I had to completely wipe a laptop drive after visiting just one MP3 site last year.
Forget that.
Now I just buy the CDs even if I only like one song on the whole thing....:)