If you follow these kinds of things, you will realise that AV technology is getting worse not better at protecting you from malware. Case in point, yesterday I downloaded a file from a rather dubious site. I checked it out with ClamAV and McAfee and both gave it a clean bill of health. On running it and monitoring it's progress with process explorer I realised pretty quickly that it was malicious. I submitted it to VirusTotal and it was found to be malicious by only 3 scanners (all free, none of the 'big vendors' detected it) and at least two looked to be using heuristics to make that analysis.

Now it seems the automated classification debate is heating up with Havlar's recent work, and now Microsoft's Anti-Malware team (and Havlar's response).