Daring Fireball has a great post on Boot Camp
Boot Camp is not about world domination or a direct frontal assault on Microsoft’s Windows monopoly. No matter how cool Boot Camp is, it’s not even going to make sense to most people out there, let alone actually get them to buy a Mac. You try explaining "boot loaders" to your mom.
But Boot Camp is inordinately appealing to the higher end of the market, the enthusiasts. Your typical civilian (i.e. non-enthusiast) has no need — or at least sees no need — for dual booting. They use email, they use a web browser, they want something useful to happen when they plug a digital camera into their USB port. Whichever OS comes on their computer is good enough for this.
But there are all sorts of uses for Boot Camp for nerds. Any sort of Windows-only software, for example, is no longer an excuse not to buy a Mac. Like, say, games. And for many of these people (i.e. the enthusiast/nerd/"into computers" market) using Boot Camp is free because they already have Windows XP installation discs sitting around.
I would add to this that Boot Camp now also make Macs much more appealing to households with different types of users. Though it will take time for word to spread, as households with both simple users who want something that "just works," and office drones who want a system that talks pretty with their corporate IT environment get wise to Intel Macs, you're going to see widespread adoption.