i've asked this before, but for some reason or the other I don't think it was replied to (or maybe i don't remember, which is more likely) --- do we HAVE to cancel them? I used mine a bit, the reception absolutely sucked so I sold it on ebay (to be honest I wouldn't have kept the service, as I have verizon, so I ended up paying $50 over the weekend on a cable to connect my timeport to my laptop).
I was always under the impression that it just stopped working after the trial...
I had a friend who got one of these from me that had not been deactivated, and was still registered to the number on the box, in my name and address on the website. You enter the phone number of your account from the box and password and it will give all your account details. This card he got had expired with free minutes (2500), and would not work any longer, but when he tried to activate it in his SprintPCS account, they told him since it had not been deactivated of my number, he could not activate it until I did so. I did following the previous instructions in this thread (or was it another on this topic?), and he was able to activate it then. Those people who bought them already pre-activated (as you received them) on fleabay etc. may be using the modem under your demo account with the free minutes, but when they stop working and they need to activate it, they will surely run into trouble from my experiences. Besides, who wants an open account out there open in your name (or alias) and address. You should deactivate before selling or giving it to someone or chance running into problems later on when they want to use it past the demo time.