I would guess that the "Internets Generally Accepted Theory" states that the hardcore pre-order and the casual do-not.
This flies in the face of the data we are seeing here however as it appears the more casual of the two new hardware offerings (Kinect) is briskly out-pre-ordering it's more hardcore competitor.
I thought I had read somewhere that IOI had an article pending on the Move/Kinect pre-sales. I'd be very interested in reading that.