[Stuart]

I think the main reason companies limit the amount of devices/oses they support is simple. Training. You can't train someone to do even basic support on every device the customer is likely to plug into the network because the number of possible choices is too great.

On the computing side, we have Windows, OSX, a lot of Linux distros (and there are a lot), a few BSD clones (I count Darwin here because configuring it is different to OSX), and various flavours of Unix.

Then you can bung in the PS3, PSP, Wii, DS (probably, not sure if it has a web browser), iOS based devices (iPod touch, iPad, iPhone) mobile phones (Android, Win Mo, Symbian and any with custom firmware or customised interfaces) and other web enabled media players.

You could also add in an increasing amount of TVs, Blu ray drives etc..

Very quickly, you could reach hundreds of products the person needs training for, all of which have their own methods of setup.

Mind you, even within Windows, you have manufacturers that insist on installing their own networking software , so there can be hundreds of variations there..

At work, we offer a wireless network, but we have been told we can only officially support Windows machines running the official windows wireless software, OSX, and iOS based devices. We are free to offer help on other devices/oses, but are not required to..