I think Nokia is using a magnetic switch on the back of the screen and on the inside of the case, rather than other mechanical switches (i.e. plungers, etc.) as the magnetic variety will not get filled with dust, etc. I had noticed the same behavior but had not yet gotten the time to write it up. A magnet also holds the kickstand in place... On the N800 a magnetic switch would tell the unit when the back-plate was on or off. It is a very clever way to do it. I would suspect that the camera may work in a similar fashion (although I have not tested that yet.