The fact of the matter is, if you know what you're putting into your computer, YOU YOURSELF is the antivirus, you are the filter, and yes, you don't need an antivirus software if all your sources are legit.
But just look at the last few pages in here, from people asking for cracked versions of an app, to "who buys Blu-rays, just download them" mentality, how on Earth would you legitimise and make sure these "sources" are not compromised? I would figure if anyone here is so BOLD to claim that you don't need antivirus programs, they're sticking to approved, safe and clean sources, then yes, I would agree that you don't need antiviruses. The question here is, is everyone here sticking to the clean sources or not?

So please, get off your high horses and stop thinking that you're immune. A simple rogue keylogging software embedded after you've "visited" your favourite Megaupload/Rapidshare/etc site on your supposedly safe Alienware ,while you're "supposedly" safe and going about your business buying stuff online, or purchasing games through Steam can easily compromise things later, from something that as mildly annoying as "slowing down your computer" or as devastating as identity theft/CC fraud.
Bottom line is, you wanna be antivirus-less, watch where you're surfing and downloading/installing stuff into your Alienware. Question is, with the laidback, "who cares where I get these files as long as I got them" attitude/mentality I see around here, is anyone practising safe netiquette like how you're practising safe sex these days, or is all this lip service?