I would add a new entry that I would name " Reward hunting ". It is the method when you are active in more than one BTC related communities and are monitoring the needs of people who are offering reward for some casual thing then be the quickest to accomplish it for them.
But is is not something that can be done on a daily basis, it is totally random thing, somewhat lottery. I wouldn't call it reliable way of earning BTC.
It is the same a affiliate hunting - if you are lucky you will earn, but most of the time you have zero profit.