I had a colleague who worked on a side project that was no where close to the main business of the company but was related to a "hackathon" type project at the

I had a colleague who worked on a side project that was no where close to the main business of the company but was related to a "hackathon" type project at the company that he was uninvolved in. His side project took off and he quit to work on it. The company successfully sued him for millions of dollars. This was in the US but not in California.