OK, well its a reason even if not a good one. For those who aren't incurable geeks like me, you'll need to understand that the new Apple PowerBook have a motion sensor built in that detects orientation and g-force changes — it's a way to keep the data of chronic laptop-droppers safe.
But what happens when you hack the system? That's exactly what was done here... take a look at the "Perturbed Desktop" movie, here to see why you'd want to start walking around or taking canoe rides while using your PowerBook. With this hack applied, you would never again need to leave your PowerBook at home while visiting the Fun House at the local town fair.
This is what being a geek is all about.