Actually I was the same (while I was running a Windows box). I used to work for an anti-malware company too, and my experiences there pretty much agrees what everyone says about Norton / etc...

I don't open attachments from strangers, I don't have warez on my computer, and I call / confirm when I get a word doc. (It doesn't matter because I do the conversion on googledocs anyway).

I know not everyone is fortunate enough to do all of that, but it is entirely possible to avoid viruses if one really wants to.

Not anymore. If you receive a targeted attack or a 0-day attack vector through a firefox, pdf or even libpng vulnerability, the only real way you can be safe is to unplug your computer from the internet.