Biggest way to win is through educating users on what the heck they're doing.
Any1 can buy a pc and get internet service - the majority will be virusized within a matter of days.
U can install urself to the hilt with Norton/McAfee/ZA/AVG/NOD/etc, the apps and OS of the mainstream pc is too wide open for stuff to be adopted by ur pc without ur permission - which is ironic as when they want to do things themselves, the latest OSes complain asking for admin rights. None of them really are worth their salt to the unsuspecting user. The average user would possibly use them ok and I'd expect the more experienced to use just free av stuff. Those with 20 years of netting could/should get by with nothing installed at-all as they 'should' know where and what they're doing with both email and websites.
Anti-viral company's will be licking their lips with excitement.