Just a few hours later, TechCrunch is reporting that Twitter may have signed a term sheet with one or more venture capital firms that would value the microblogging company at $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.

Facebook supposedly made an offer to buy Twitter last fall for as much as $500 million dollars and was turned down. Though in fairness, most of the deal was for Facebook stock, not cash.

Twitter has been searching for a way to “grow up” and actually figure out a revenue stream that fits with its growth. This new round of VC should give them plenty of time to discover that. It should also take a lot of pressure off of Kevin Thau, Twitter’s newly hired biz-dev guru.

• Twitter Lists, Robert Scoble, Chris Brogan and You: A Self-Help Tutorial
• Twitter Outage Happening Again: Could be another DDoS Attack
• Brizzly: What Twitter would be with a Facelift and on some Steroids