It seems that having good antivirus software isn't enough anymore. In 2008 Panda scanned approximately 67 million computers looking for malware infection. Of all those computers 35 percent were infected with malware and they were running up to date anti-malware software. Of course, if you gain enough information about safe Internet use and apply it appropriately then it can be used to protect yourself - but people don't do that. So they blindly rely on software that can't protect them either.
source: windowsitpro.com