I tried it on my PowerBook, and part of the problem users might be facing is that you have to hit it with some real force if you "tap" the screen as in the video. At the sensitivity level of the "tap" I think most people would feel comfortable using on their $2000+ computer, someone with a zealous space bar/return pounding habit would also register in SMS, especially if being used on a bed or a lap.
This would be better for the display frame/hinge/computer in general if it responded to tipping and not smacking.