If you borrow my computer and mine bitcoin and that bitcoin generates value for you in excess of what you pay me for renting my computer then you've created surplus value, and that's not cool at all, man! Think of it as borrowing a man's hammer. Its no different. A guy borrows a hammer, builds a few houses, charges rent, and one day owns the whole the city!! That's f@#$ed up!
I do not bitcoin yet but I do Ethereum and transferred some money to my account for the purposes of doing bitcoin in the near future should another buying opportunity present itself.
I think ETH looks like a decent hold in the mid-term and BTC represents an attractive day short term trading option. Crazy volatility. I'm also looking at LTC which seems to track BTC but with a healthy lag. This run up in crypto currency values is ridiculous. Still figuring out how I want to approach the game.