His response: "The quarterback for the New England Patriots, Tom Brady, is not on Twitter, and I would like him to be on Twitter."
Costolo was participating in a keynote conversation at the conference in San Francisco. He said he, like Brady, went to Michigan.
After the session, Costolo expanded on his comment, saying, "I'm a big Tom Brady fan." He also said he was a Patriots fan, a 49ers fan and a Bears fan.