While speaking at the Web 2.0 Summit in San Francisco yesterday, Twitter CEO Dick Costolo revealed some new and interesting stats about Twitter, including a huge leap in daily tweets sent on the platform, how the iOS 5 integration on Apple’s iPhone has boosted signups, confirmation of Twitter’s heady valuation, and a lot more.

Costolo unveiled a plethora of Twitter news and statistics, including:

  • Twitter is now seeing 250 million tweets per day – This up from 90 million in September 2010 and 140 million in March of this year. Every 4-5 days Twitter serves a billion tweets
  • Twitter has 50 million daily active users – Twitter has 100 million active users in total (note: Twitter has around 254m total users), but only 30% were active on a daily basis in January of this year. This is now up to 50%
  • New signups tripled when iOS 5 launched – Twitter is now integrated deeply into the iPhone’s iOS 5 operating system, and new signups went up three times when iOS 5 launched last Thursday. “iOS was absolutely huge for us,” said Costolo. “We all anticipated it’d be big, but the integration is so native and feels so frictionless. It was even better than we thought it was.”
  • Twitter is worth $8 billion – This number has been floating around for a while, but Costolo confirmed it on-stage. (It’s worth noting that a CEO’s valuation of his own company is not the same thing as the market’s valuation.)
  • Twitter’s secret is its simplicity – Costolo thinks that Twitter will outlast Facebook and Google+ because the platform has stayed true to its roots, which lie in its simplicity, and that success in the future means keeping things basic. “We think we can reach every person on the planet, [and] we think the way to do that is to simplify it. Over time, Google+ and Facebook will be different than the experience we want to pass onto our users.”
  • Twitter: the public/private network – “We’re the free speech wing of the free speech party,” said Costolo, noting Twitter’s stance in protecting the privacy of its users by allowing anonymous profiles and the company’s stand-off with the US government over their investigation of Wikileaks, “We respect and defend the user’s voice.”
  • Twitter’s IPO – Don’t expect this anytime soon, says Costolo. “We don’t want to have to be beholden to an IPO window. I want to go public when the company’s ready and prepared, and not at the whims of some window.”
  • Twitter’s business model – Twitter ads in the future could include richer media, such as video and interactivity, but Twitter is in no hurry to rush those out. “We’re growing the business in a way that makes us proud. We’re growing in a way that’s sustainable and scalable.”

Costolo was also pressed on the future of Twitter search, and whether users will ever be able to fully access their history on Twitter.

“We want to be able to access old Tweets and old DMs, we just have to prioritize the work,” he said, adding that Twitter has a finite number of search engineers who are currently working on other challenges. “It’s just a matter of priorities, [but] we need to get to the point when we’ll be able to do this.”