if you're a smart browser, you don't really need to use any AV at all.
People who actually believes this are the ones who are to blame for the tens of millions of machines currently compromised in the US alone.
Remember Tom's Hardware? Remember WL Messenger? Remember Anandtech last March? Just three high-profile examples of how someone purchased advertising, and then proceeded to utilize their ad script to infect systems and do drive-bys, etc. Have you paid any attention to what's been going on with Twitter lately?
Of course, some people will actually click hyperlinks in their email messages from people they know with subject lines like "Here you have..." and install a worm or trojan.
Malware writers are always thinking of different ways to get you infected. Things like pr0n and P2P are pretty low on the totem pole these days for spreading malware.
Don't want to use AV? Please pull your tap.
While I agree that the whole "Common sense is all I need" mentality does not quite work, anti-virus software just isn't the be all and end all. Fact of the matter is, anti-virus software is always one step behind.
AV can compliment other security software. I would recommend something along the lines of sandboxing software, like SandboxIE for example, if you really want something preventative.
