It'd need some smart design. The idea of a camera mapped to motion seems obvious, but at the same time you'd have an awful lot of wiggle in a lot of cases! One of the PS3 devs said they encountered this very problem. Consider how the Wii cursor tends to jiggle about a bit, and imagine that applied to the whole camera...
So you'd either want some serious filtering, or...um, not use it at all I guess. In Wii's case it works well to use the motion for aiming a cursor. Sixaxis isn't as well suited for pointed a direct screen position. At first I was very keen on the idea of camera mapped to motion, but sensitivity is a major concern. If they can get it to work well, it'll be excellent, but that's the 'IF' that's hoding things back.
As for moving controllers about, that's not an issue, because when your motions are mapped to the game, you'll adopt different behaviour. eg. When using PS2 I might move my hands all over the place. But when playing a ball-in-maze tilt game, my motion control is extremely focussed. Likewise I'm less likely to shift around when using a PSP. If moving the controller affects where the camera moves, you'll learn to keep your hands still. It might be a bit tiring, but you probably won't notice while actually gaming. A bit like controller cramps in the hands! I can play for a long period, and then when I put the controller down I notice how stiff my hands are. When playing a motion game and focussing on not moving the controller unnecessarily, it'll be when you stop playing that you'll notice how stiff your arms have become from keeping the same pose!
However, that'll tie in with the problems in inital experience. Before someone's learnt to curtail their natural jiggying about, the camera or other control will be a mess and the player will just be frustrated with the control scheme and curse aloud 'why the %&*@# did they use this ?£$*&! motion control?!'