My former landlords had an issue with their open network. People used to get on and lock it on us. Even when I left it was still open. Really silly on their part.At a place I used to live there was a wireless network named Dlink ... of course completely open and configurable. Anyway, after using that network for a while to download from newsgroups and such the owner got wise and secured it and renamed it to Not Your Dlink.
Hope that never happens to me, my password is an insult to the boss.
If its a work computer you do realize they have the right to see your computer. If they ask you have to be able to hand over your password.