CouchDB is a pretty well-known "didn't get accepted, but kept going anyway" project. Not really a business success story, but it is a project that has had an impact on web technology, and on a scale that many YC companies have not. It's an Apache Foundation project now, but I don't know what that means for its business case.
And, of course, several teams have been rejected once or twice and then gotten in later. A few have even blogged about it; notably wheels of Directed Edge.
And, of course, several teams have been rejected once or twice and then gotten in later. A few have even blogged about it; notably wheels of Directed Edge.