What is your employee-employer agreement (if any) in regards to developing and possession of personal code written outside of work hours that directly competes with your employer's code, even if the personal code does not contain any of the employer's code (and vice versa)?
It can become a big issue when the programmer leaves the company and just realizes his personal efforts suddenly became the property of BigCo.
edit: uh, that could've been phrased with much more eloquence, but you're gonna have to live with the ugly, unrefined version.