Not really, as Dell would have a bulk licence key allowing them to install WM5 on any device they make, and manufacturing quotas are easy to show. Every device would be accounted for so they could show how large a licence they are paying for, the sticker is just there so you can say "Hot damn, I've got an official microsoft product" or, in simple terms,

:approve:
You'll still technically have a licence, through Dell, you just don't have the paper.