Suppose this concept was used for good instead of evil. Suppose someone were to set up a benign bitcoin miner that individuals could volunteer to install and decide how much unused cpu time they were willing to allocate. Suppose, say, 85% went to some charity and 15% went to "admin overhead" and suppose people started deducting the expense as a charitable donation? Perhaps the donor might even get a bit of a cash rebate?
Interested in working it through? Email me.