The ego is the driver making the decisions. It decides between the devil (the id) and the angel (the super-ego) on either shoulder (yes, all those cartoons you've ever seen are partly true). We have voices in our mind, and it's up to the ego to decide which one to fulfill. Its goal is to satisfy the id in some way while also attending to the super-ego.
Great article, I have tried a few over the years. I had a side business cleaning offices for years. It did great, but I hated never being able to take more than 3-4 days vacation, so I eventually gave up. I tried MTurk, but if you multiplied my earnings on an hourly basis, it was a little over $6/hr. My blog is much worse, probably less than $0.25/hr.