After months of speculation, Twitter confidentially filed an S-1 with the Securities and Exchange Commission Thursday evening. Naturally, the news came by tweet: 

 

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.

CEO Dick Costolo, who spoke on leadership at the TechCrunch Disrupt conference this week, declined to take questions afterward, leading many to speculate the company was already in a "quiet period"--that timeframe when start-ups preparing or expecting to file paperwork with the SEC are asked to stay mum so as to not prime the market.  

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.