I think the best anti-virus is your fingers, and keeping your private network and personal computers, just that.
I don't let people use my wifi and I don't let them touch my computers. I also have not run AV since windows 98. I do run windows firewall now, but that's only because it came in one of the windows updates, and I have been too lazy to turn it off
Primarily because it has not affected my day to day workflow. I doubt it works anyways. Careless? I don't think so. I think it just makes me even more careful in my clicking patterns.
I will say that the last virus I got was not from clicking though. It was from connecting to someone's unsecured wireless network so I could get my laptop online for a few minutes. I think it was mytomb or mydoom or something like that that was somehow to infect every computer on a specific network, it was very noticable and reletively easy fix.
I use trend micro's online virus scanner if I suspect infection and typically all it finds are attachments in my email box that have never been executed.