Sometimes, you hear comments like anti virus is dead. It all depends on who is saying it. One thing is for sure, AV vendors have a tough job today. Keeping up with the bad guys is harder and harder everyday. They are producing more and more malicious software and some of the software they write can even change slightly so that the electronic signature so every time the malicious is written, it changes slightly.
I don't believe AV is dead. It has its purpose. There is enough malicious code floating around on the Internet for the script kiddies to get a hold of, it is a good idea to have AV. Many times when reading the Internet Storm Center's website (isc.sans.org), they will post documentation from a site I use where you can submit a file that you suspect being malicious(www.virustotal.com). It takes that file you suspect and run it against 33 anti virus engines and it documents if it is detected. Many times, only one or two actually detect it.
When trying to keep up with those really smart bad guys, AV has a more difficult time. I have always said that your behavior when browsing the Internet can either protect you or get you into trouble. Always use AV, use a firewall, and keep your signatures up to date so you will be able to detect that malicious software.
Stay safe and take care. Rock Chalk!!