It's kind of interesting how Linux fans brag about all of the software that comes pre-installed with every Linux distro but bitch and moan if any extra software is installed on a Windows box. Why isn't the software that you'll probably never use on a Linux box a bonus but gets called bloatware on Windows? I'd personally rather start with a blank slate or a standard image with standard programs that are always used by everyone (PDF reader, Office suite, Flash) than have to go through to uninstall a bunch of shit I won't use.
I'll tell you the main reason my company doesn't use Linux and restricts its usage - because it's FOSS. The integrity of the code is, at best, shaky. I'd also say that having an anonymous FTP, SSH, and HTTP server running on a box right from the get-go is a giant security hole and should be plugged up quickly if it won't be used. Also, have you heard of Windows PowerShell? It's pretty much the bee's knees for a shell (and is secured by default) and comes standard with Win7.
In a properly secured corporate Windows environment (basic AV/malware scanner and non-paper thin firewalls), malware is a non-issue and easily caught to be fixed. There's multiple good solutions for pushing non-MS software updates, Lumension being a step above the rest.
In a home environment, Linux is good enough for most anything except bleeding edge gaming. Gaming is a huge market for computers. Something that Linux cannot compete in without Wine which only works sometimes with some games and not easily configurable for the average end user. Most of Linux is really just not very friendly to your average end user even with a lot of the improvements I've seen the Linux desktop go through over the last decade. It's friendly to techies and computer savvy people but to average people, there's a steep(er) learning curve compared to Windows. Who here that installed Linux for their grand/parents didn't have to sit and show them some of the basics for getting around that would've been fairly intuitive on Windows?