Twitter raising $400M round, valued at $8B

Micro-blogging service Twitter is in the process of raising $400 million in funding that would value the company at $8 billion, according to a report by the New York Times.

The site has more than 300 million registered users who fire off quick messages, called Tweets, that are less than 140 characters long. The company was valued at $3.7 billion after its most recent round of funding in December. Twitter makes $200 million each year, according to analysts cited in the report.

The funding round will be led by Yuri Milner and Russia’s DST, the investment company that has backed Facebook, Groupon and Zynga, according to the report.

Twitter users sent two million tweets a day in January 2009 and 65 million tweets a day on average in 2010, the company said. The site’s users now send Tweets more than 200 million times every day.

While the site is incredibly popular, it has had some trouble finding effective ways to monetize the service. The company introduced “promoted tweets” last year in an effort to make money and it also runs promoted trending topics.

Twitter recently purchased TweetDeck, a mobile and desktop application that lets Twitter users access multiple accounts and post messages on them simultaneously. Twitter also bought iPhone client Tweetie, transforming the application into its main mobile Twitter app. The company works directly with photo-hosting service TwitPic. Twitter is also encouraging external developers to focus on something other than straightforward Twitter clients.