I don't think spending your evenings on a startup is necessarily bad for your employer. Someone spending considerable amounts coding on his/her startup in the

I don't think spending your evenings on a startup is necessarily bad for your employer. Someone spending considerable amounts coding on his/her startup in the evening still brings the knowledge and experience of doing that back to the full-time job. At home you're working on projects you care about, you invest time in learning about new technologies, you research best practices, etc.. That actually adds value for your employer compared to those employees who go home to the wife and kids and don't spend any of their free time thinking about code. Ofcourse, you shouldn't overdo it and arrive at work a zombie, but that would also have a negative effect on your startup work, so I don't expect people to actually do that.