[jloughry]

It's debatable whether all Bitcoin miners are doing it for the reward, or whether some are doing it for an idea.

On the one hand, I think I'm doing it to help the network, but on the other hand I kept the pitiful few coins I've got thereby, and didn't give them away. Why do I keep Bitcoins? Not as an investment, surely; I think of Bitcoin as more of another currency that I keep some money in all the time, like £ or €, so I can buy stuff when I'm there. But my little Bitcoin mining operation is being run for the purpose of "transaction security auditing" [thanks, qnr!] for the same reason I run a tor exit node: because I want to encourage such things to exist.