I would probably be Software Engineering even if my employer didn't pay me to. As evidence, note that it's new year's eve and I'm writing patches (and waiting for tests) during my holidays for someone else's FOSS project I'm contributing to :).

I my employer didn't pay me, I'd stop working on their projects. But in the meantime, I enjoy my profession (at least most of the time) and get paid. If I had enough money then I'd stop working on what my management wants and work on stuff that I want to work on. And I have to imagine that at this point, Buffet is also doing whatever he wants to.