When users would be able to download or export all of their Tweets:
"Before the end of the year," Costolo said, receiving a hearty round of applause from conference attendees. However, he also added a note of caution to his prediction.
"That’s the CEO saying this. Not the engineer," he said. "The CEO’s perspective is, I would dearly like to have that out by the end of the year."
Twitter handling requests for users' information from governments across the world:
"We’ve got to figure out how to deal with that on a global basis," Costolo said. "It’s something we have an enormous amount of people and resources assigned to."
Earlier this week, Twitter complied with a Manhattan judge's order to hand over Tweets from Occupy Wall Street protester Malcolm Harris, who has been charged with disorderly conduct after allegedly using Twitter to rally demonstrators. Twitter had unsuccessfully appealed an earlier order to turn over the Tweets.
Costolo said the Tweets were sealed in hopes that Harris could appeal the order, adding that the company "strongly" believes in fighting against efforts to force the company to turn over user information. But it has to balance that belief against the rule of law.
How much money Twitter is making:
"We don’t talk about our revenue," Costolo said. "One of the benefits of being a private company is you don't have to explose how the business is doing."
Twitter's popularity and his job:
"You wake up every morning and it’s fun to go to work," Costolo said. "I’m never going to have another job like it."
The CEO said he enjoys receiving emails about users across the world who are commenting political issues as well as topics ranging from "the ridiculous and sublime."
As an example of "ridiculous and sublime," Costolo pointed to these recent Tweets about cable television from two "Star Trek" captains:
"(Twitter users range) from that to the president of Rwanda, Paul Kagame, answering questions to consitutents and people around the world," Costolo said.
What Twitter is working on:
Costolo said the company is looking at ways to better curate Tweets about real-world events. He also said it sees an opportunity to build on how its users Tweet about television.
The possibility of a Twitter phone:
"We don’t have any plans to do anything like that," Costolo said. "It’s not the way we see the future of the company."
Who he'd like to see using Twitter:
"The QB for the New England Patriots, Tom Brady, is not on Twitter. I’d like to see him on Twitter," Costolo said. Both Brady and Costolo attended the University of Michigan.
Banning a well-known talk show host from Twitter:
"Is it possible to have Piers Morgan removed from Twitter?" asked the Columbia Journalism School's Emily Bell, who was interviewing Costolo. Morgan, the host of "Piers Morgan Tonight" on CNN, is known as a prolific Tweeter.
The question drew laughs from the audience. Costolo didn't answer, saying instead that "I had no idea I'd be the straight man" during the interview.
Morgan later responded on Twitter by referencing the handle of the company's creator and co-founder Jack Dorsey: