Yea true, but i'm imagining that the friction might be so minimal that it could walk for a long time. i don't know though, but it does seem to be able to conserve its momentum pretty well.
It's wind powered to I don't thing giving it a push would make it work indefinately. Amazing how he applied his concept (of the limbs) to a massive ,metal sculpture and it too works. I'd love to build something like these