Tomio Geron

It all started with a “stupid” idea and a message about pinot noir.

Two of the founders of Twitter Inc., Evan Williams and Biz Stone, talked about how the micro-blogging service began, the challenges it faced and an eventual potential IPO, at Startup School, an event organized by Y Combinator held at the University of California-Berkeley on Saturday.

Twitter investor Ron Conway responded sharply to media moguls’ criticisms of the short-messaging service and related start-ups that haven’t so far been big revenue generators.