Luke points out some of the disadvantages of running Windows.
As a friend of mine mentioned it is possible to get 0 errors back from ad-aware by using your computer smartly (not running IE, watching cookies, changing your security zone, not running as admin), but in my opinioin this isn't the way that most "normal" people work. They turn on the computer and use what is available, click on pop ups, click executables that come in email, and are blissfully are hosts to adware, spyware, worms and viruses. The number of worms and crap that float around support this theory :)
