Everyone has their eyes on Twitter. According to the Wall Street Journal's Spencer Ante, the short-form messaging service "has become a very attractive takeover target, with some estimating 2011 revenues at $100 million and a potential takeover value of nearly $10 billion." Who wants to buy? A number of companies have had talks with Twitter representatives, according to Thursday's story, but Google and Facebook are the clear favorites.

Both Google and Facebook have discussed buying Twitter in the past and have kept their lines of communication open, people familiar with the matter said. One of these people said companies including Facebook and Google have expressed "latent interest" in an acquisition.

On Wednesday, venture-capital firm Andreessen Horowitz said it had bought more than $80 million of Twitter shares through exchanges for private-company stock. A spokeswoman for Andreessen Horowitz declined to say what percentage of Twitter those shares represent.

Twitter's revenues and valuation have risen even as the company continues to work on ways to translate its more than 200 million registered users into a profitable business. Twitter, which was created in 2006, introduced advertising into its service last year.

One of the new Twitter ad services, called Promoted Trends, has been selling out its inventory every day, said one person familiar with the matter. The other two ad products, Promoted Tweets and Promoted Accounts, are also doing brisk business, this person said.

Despite the high valuations, Twitter's executives and board are continuing to work on building a large, independent company. People familiar with the situation said the company believes it can grow into a $100 billion company.

To do that, Twitter has been hiring engineers and increasing its work force to more than 350, up from 100 in January 2010. Twitter has also been building an executive team, appointing Mr. Costolo, a former Google executive, as CEO last year.

Read the full story at the Wall Street Journal.