If you think of a virus as being something that replicates itself, spreading from computer to computer, until seemingly everyone has it installed, then maybe you could classify Google’s Gmail service as being one.
If you happened to be using Microsoft Windows Live OneCare security over the weekend then it would have done the classification for you. Yep, OneCare users who visited their Gmail account were being warned that their computers had been infected with the BAT/BWG.A virus. How do I know this? Well although as a UK based user I should not be able to install OneCare courtesy of some strange tribal culture thing going on at Microsoft US, by changing the language defaults on one machine I was able to fool the installer into thinking I was an American citizen and therefore trustworthy enough to be blessed with the security system. I have also been a fan of Gmail ever since the very first stages of the Beta, and have numerous Gmail accounts as a result. Note, I said Gmail because these accounts were established before the lawsuit that resulted in Google being unable to use that name in the UK and so switching to Googlemail instead.