Whoever is paying the electric bill. You see lots of people talking about mining from apartments with included utilities, dorm rooms, their work, etc. It sounds like 21 Inc. wants to take this route on a massive, distributed scale.

Wasn't there also a company that pre-sold mining rigs, used the pre-sale money to fund the manufacturing, and then used the equipment to mine for a few months before shipping, at which point the equipment could no longer profitably mine?

Was that Butterfly labs? I remember hearing rumours of their early ASIC business operating that way.