When I think of a 'serial entrepreneur' somebody like Keith Miller comes to mind. Since I've known him he has always had some sort of side project going on (some of which seem crazier than others). In the end it's been a pretty logical progression to where he is now. Passion is what drives him, and he's most passionate about soccer (which if you know Keith you already knew this). I always love when people can turn their passions into how they earn a living.