A couple of weeks ago IAC Chairman and CEO Barry Diller was telling the elite crowd at the Allen & Co. Sun Valley conference that he was "pessimistic about Twitter’s prospects for making money." A couple of weeks later and he's singing the same tune, this time to the elite crowd at the Fortune Brainstorm Tech conference in Pasadena.In an interview with Andy Serwer, Diller admitted that he didn't really understand the service and doesn't use it himself. He said it was for people who want emote real time information like "I'm going to the doctor now," "I've left the doctor now," and "I have a cavity," and that it doesn't seem like a natural advertising platform. "It's not exactly for me" he said, "I don't go to the dentist."The full video is below: