A porker: will not fly
1) Right now, people *think* they want Windows: it's the devil they know. I continually try to persuade my computer-incompetent relatives to let me set up Linux or just go buy a Mac, but they won't. Even when they go from XP to Vista and everything breaks, they won't switch away from Microsoft.
2) The point of the Web, especially the Cloud, is universal access. Many of us read our daily news or email on a home PC, on a work PC, a smartphone or MID, maybe a set-top box. Browsers are bursting out all over (did you know there are TV's which run Linux internally, just for fun?) and the future will only bring more. Are these all going to run Chrome OS? Consumers aren't going to like the idea of a 'special PC' just to have access to their email and documents.
3) Drivers, drivers, drivers! The entire market for add-ons in high-street stores (from printers and webcams to USB coffee warmers) is based on the fact that a Windows driver is all you need. (Linux people write their own, and Mac people wouldn't be seen dead in PC World anyway). Cheapo tat-makers won't want to write a whole extra driver unless the market is huge, and Google won't seemingly allow them in the OS anyway.
4) They are fighting Microsoft on their home turf. Look: Asus's initial EEE had a Linux distro, which cost them nothing and offered them total control. Now XP has taken over, despite costing money per unit and ceding control to Redmond. I don't know how they did it, but if a completely free (as in both speech and beer) OS couldn't hold out, how will Google's offering do better?
5) The 'security' aspect is completely bogus. There may well be no malware for Chrome OS - yet. But as soon as the whole Chrome ecosystem acquires value, it WILL be attacked one way or another, and frankly I trust Google less than Microsoft when it comes to security.