Off the top of my head and as anecdote, I've probably received the most spam and/or malicious emails from friends compromised email accounts where those accounts are Yahoo accounts. Hotmail would probably be second.<p>I usually go to the effort to call them up as soon as I can to inform them of the compromise. I've started gently describing the problems with these particular hosts; unfortunately, however, most don't go to the effort to make a change. And several have been compromised multiple times.