joe - this was my first reaction also. but then i read this N&V article... they put the batteries in the 'head'... and consider the segway... sure the batteries are in the base, but the center of gravity probably is closer to our mid section when it is being ridden...

i get the impression that a high center of gravity is important.. i also notice that most bots put the accelerometer low, near the wheel axle height...

if anyone has more info.. i am reading along.. interested in the concepts, if not actually making my own balancing robot!

i know it may sound like sacrilege, but try the parallax forums.. very helpful people there...