Dana's security blog has a pointer to an article which notes that Readers Wouldn't Buy Security Products From Microsoft. I'm in total agreement. Lots of interesting comments on this one, with many good points. As I noted elsewhere, Microsoft can't write a word processor that isn't vulnerable to attacks and viruses, why should people trust them to write security software. They write user friendly OSs and decent applications, but much as they'd love to sell you otherwise (and I'm sure they will be telling people how wonderful a security company they are as much as they are starting to hype Longhorn), they should stay out of the security market.
Sadly, they probably won't, and will go in with all their resources, marketting, bloggers and programmers and probably squeeze some of the security vendors out of the market (ie: zonealarm) as they try to sell us on the "no, you can trust us this time" marketting hype that's no doubt coming.
As Dana noted they have a chance with Longhorn to prove they can create a secure OS. It'll be here in 2006 (or later), so you can see that as either a huge opportunity for security products and/or alternative OSs to jump in, or sad because the people that are being hit by viruses and worms aren't the sort of people that do anything to their OS from the time they buy their new computer (ie: the stereotypical mom, dad, granny and grampa).