Twitter Inc. has reportedly raised about $20 million in new investments based on a valuation of the company at up to $250 million. It's likely they'll raise more than the $20 million in capital they've taken in over two previous rounds. Their last round, raised in June 2008, was a $15 million raise from new investors Spark Capital and Bezos Expeditions. Union Square Ventures and Digital Garage increased their previous investment.

At the time, the company had about 2 million users and the company was valued at between $80-to-$100 million. Since then, the number of Twitter users has increased to 6 million. A majority of Twitter’s usage is through its API and the unique visitors to its website are only fraction of company’s growth story.

Moreover last fall, Facebook was said to have made an offer to buy Twitter worth as much as $500 million. The new valuation of the company is about half what Palo Alto social networking company Facebook Inc. reportedly offered for Twitter, although most of that was said to be in Facebook stock which today is worth nowhere near what it was thought to at that time. Facebook's valuation was pegged at about $15 billion when Microsoft Corp. invested in it in 2007 but is now valued at less than $5 billion.

This new deal to-be means they’ll eventually have to look for an exit at much higher price than that, since their new investors will want a significant return on their investment. However the service is still growing at an impressive rate and with celebrities like Shaquille O’Neal, Ashton Kutcher and Jimmy Fallon now using it regularly, it seems on the verge of breaking into the mainstream.