Given the confidential nature of the S-1, made possible by the Jumpstart Our Business Startups Act, one can only guess at Twitter's current revenue or major investors. Twitter, which has 200 million active users, must have less than $1 billion in revenue because that's the cap imposed by the JOBS Act for companies wishing to file confidentially. To date, Twitter has taken $1.16 billion in funding.
In recent months, Twitter has made a number of acquisitions that seemed to indicate its interest in proving its revenue-generating potential to the market.
On Monday Twitter announced it picked up MoPub, a mobile ad/exchange/publisher network, for $350 million in stock. Additionally, Twitter bought Trendrr, a company that tracks social media engagement around televised content, for an undisclosed sum back in August. In theory, Trendrr will help TV advertisers reach people who tweet while watching.