I think the main difference between a weekend project and a startup, is a startup explicitly has the goal of becoming a sustainable business. A project is just

I think the main difference between a weekend project and a startup, is a startup explicitly has the goal of becoming a sustainable business. A project is just a project; throw something at the wall and see if it sticks. A minority of really sticky projects may have the potential to become startups. :-) [edit: and conversely, some startups may have been better off left at the project stage. :-P ]