I doubt many japanese take those on the subway though! I don't recall seeing standard bicycles on the tokyo metro at all, in fact.

To the person who said you prefer to lock it up outside a grocery store - what exactly stops you from doing that with this device?

The cost is a major stumbling block; mind you, I see a lot of heinously expensive road bikes around London, and I suppose their actual utility is lower (harder to take onto buses and rail services; harder to store at home, in the street or at the office; not electric)

I'd be interested to see a study done on the device's eco credentials; I've heard persuasive arguments that electric bikes are greener than pedal powered bikes when you consider the petrochemical requirements of a pedal bike's energy source (your food)...

No subway out where I live. Plenty of older people use them because of the hills/mountains out here. You can see them on the buses that take bikes, or the non-JR train lines that let you take bikes.