I guess you are right that it's useful for black-market commerce and I suspect that's probably the only reason it has value.

Regarding this:

>Actually most of the energy comes from renewable sources, which would be wasted otherwise. The Bitcoin mining industry is so competitive, it wouldn't be profitable otherwise.

Geothermal energy isn't renewable unless it's used sparingly. Hydro-power requires huge sacrifices of land, usually fertile valleys, in the reservoir lakes. Windmills are loud, huge and ugly. Power lines require sacrifices of land. And everything needs to be produced, with the environmental impact that brings.

I'm not saying renewables are bad, they're not, but they are not so pristine that using them for bitcoins isn't a sad thing.