Back when I was doing my Rogers iPhone research, see here, I asked numerous representatives from Rogers (both on the phone and at the Rogers store) whether I would be able to use my iPhone as an iPod Touch-like device if/when I cancelled my iPhone service. The uniform answer was no! – that the iPhone would be bricked (wouldn’t even turn on beyond a warning screen) if I removed the SIM card.
Two months after purchasing my iPhone I set out to finally transfer all of my remaining contacts from my old Nokia phone to the iPhone. This required me to remove the SIM from my iPhone and put it back into my Nokia phone (the Nokia would not turn on without the SIM). In doing so, I tested Rogers’ theory that the iPhone would be completely bricked with the SIM removed. I discovered this was untrue.