So how is this a problem for IT? Simply this: If I use cool applications and hardware that I find useful at home, I'll find a way to use them at work too. In fact, I can tell you authoritatively there are any number of non-IT-certified applications on the laptops of the NWC editors. From a corporate point of view--that is, me being the face of our corporation to NWC staffers--I not only understand the need to stray beyond the corporate standard issue, I encourage it.
So what's your reality? For those in heavily regulated industries, what I've described is heresy. Desktops must be locked down, applications must be limited and the flow of information must be tracked. It's not an option, it's a business imperative.
IT Governs Best When IT Governs Less
What about the rest of us? My suggestion is to graciously admit defeat. Face it: Your users know more than enough about their computers to be dangerous--they aren't likely to be happy with corporate standards, and you're unlikely to be able to enforce them. So rather than fight a losing battle, let your users choose their own systems and offer a very broad array of software. Enforce corporate standards only and exactly where necessary.
Those standards should be surprisingly loose. Emphasize security, backup and data tracking and little else. Even applications like e-mail and browsers should be flexible: It's the data you care about, not the apps. The NWC crew uses e-mail apps from Exchange to Thunderbird to Eudora (of all things), even though the corporate standard is Lotus Notes.