3) User status on its way?
Remember AIM Away Messages? These short and customizable notes were posted on Buddy Lists in the 1990s to alert a person's friends if he or she was online, away or simply hard at work. The question for Twitter is: should users look forward to a status feature indicating when a subscriber is online, available, busy, etc?
"I don't think we'll do that any time soon," answers Costolo. Cue AOL door slam audio.
4) What happens to unused Twitter handles?
New users may find it frustrating when they realize someone already registered a Twitter handle with their name. Even more frustrating, accounts made up of precious handles may be going unused and collecting dust.
When asked if users will have access to these inactive names, Costolo said it will be possible soon, but in an "automated fashion."
5) What is Twitter doing to combat spam?
"Spam is an arms race. It always is between the technologies trying to prevent it and the spammers trying to work their way around it," Costolo said. "Spammers work where they think there are hundreds of millions people paying attention because that's where they know that they can try to have their message seen. We have an incredible technology team working to eradicate it from the platform. And the data actually show that they're doing a fantastic job."
— Written by CNBC's Eli Langer. Follow him on Twitter at