Two of the startups acquired by Yahoo in their big Web 2.0-ification wave were 'half-assed' ventures. Upcoming.org was based out of some weekend and late-night hacks, and the founders never quit their day jobs before being acquired.

del.icio.us was a one-man band for years, and even when the site started getting major attention, the founder, Joshua Schachter, was working full time on Wall Street. He says that he found ways to be productive when he had just 15 minutes free. (I recently asked him about that and he said that one of the techniques that helped was shorter methods, nothing longer than a page. That's an interesting real-world metric for how readability = value.)