If you look critically at this proposition is not far from the truth as I will explain.
If you were a Massive Corporation with an enormous appetite for computation like Google or Facebook, an efficient strategy which you could use to obtain that extra computation power without the extra cost of building another expensive datacenter would be to give people these computers to use. You could build some custom laptop computer and give it out, mostly to the academic public, for free, in exchange the recipient of the Laptop computer would pay for it by providing it power and agreeing to a term that, there will always be a low priority process running computation for the giving-company during regular use of the laptop by the recipient and the process would be upgraded to high when the user was not using the computer, in the idle mode.