[bpodgursky]

I suspect that when you get up to 250kg you run into stability issues as much as strength issues. Even if you could lift it easily, it would be really tricky to hold it in a way that you won't tip over and drop it.

[Cthulhu_]

Yeah, it'd need to be combined with research going on atm with bipedal robots; they'd have to be able to keep themselves balanced.

[gadders]

Or just have really heavy "feet". That's what the big block of steel/concrete on the back of a forklift is for.

[TeMPOraL]

Yeah, but automated balancing might be significantly more energy efficient than sticking quater-ton blocks of metals to the feet.

[gadders]

Maybe you could use the extra mass to provide super-protective steel toe caps, as per a comment above :-)