I like trying out new software (although I'm not an MS employ I'm dogfooding ;-)). So I usually download and test every beta that comes out. To do that I use Virtual PCs, as I don't want to mess up my production machine. I create these virtual machines on a removable disk so that I can run them on any PC I work. So when Microsoft released its new Windows 2008 server operating system public beta program, I rushed to download it and install it.
Unfortunately, it seems that Microsoft changed its Virtualization License scheme in Windows 2008 server OS from the Windows 2003 server one as it now needs re-activation for each PC you run the virtual machine. It also looks like you only have 1 activation per serial number as it will prompt you with an error message if you try a serial number that is already in use.
Thankfully, you can order as many licenses as you need from Microsoft's site since they're still free but this will be a serious problem (at least for me) when the server is officially released.