Today I talked with my fellow engineers about personal business ideas. I got the impression that they had spend no time in trying to implement even the bare minimum - which makes them fantasies rather than ideas.
Implementation is very important because during implementation, you become aware of technical, time and cost constraints. You also might get new ideas, it trains you in how to develop ideas. As an example, let's say you want to build a new über-coffee machine that can be installed in university campuses. Before getting into the technical details of the machine, you should call the university and see if you can talk with someone that is in the position of authorizing coffee machines on campus. Even if you get a negative response, you will have practiced talking with strangers about money and business.
I do not take seriously any idea which is not backed up by some effort. That's why I am trying things out even if they almost certainly will not become a business. They will serve as self-education and inspiration - an incubator of other ideas.