• by Steve Smith  @popeyesm, September 12, 2013

Is it possible to file for an IPO in 140 characters or less? Well, Twitter pretty much did it -- or announced the filing, appropriately enough in a 5 p.m. Tweet from @twitter.

“We’ve confidentially submitted an S-1 to the SEC for a planned IPO,” the company announced. But just to cover any legal exposure, it added: “This Tweet does not constitute an offer of any securities for sale.”

They followed it up a minute later with a picture of business as usual presumably from the Twitter offices. “Now, back to work,” it read.

By filing “confidentially,” Twitter does not have to lay bare for scrutiny details of its financial status in the initial stages. A rule change last year allowed companies with under $1 billion in revenue to keep their books confidential until the proposal gets closer to going public and the company starts pitching investors.

The IPO comes as no surprise. Twitter has been making a series of moves lately designed to build confidence in viability as an ad-driven media company. Just this week, the company acquired the mobile ad exchange MoPub reportedly, for $350 million. The acquisition gives Twitter a platform for driving mobile ad revenues and perhaps creating some unique mobile data targeting offerings. The company has a large registered, logged-in user base that accesses the micro-blog across both desktop and mobile devices. This gives Twitter a way of binding desktop and mobile identities and leveraging that data cross a large mobile RTB platform.

Twitter has also acquired two of the most important social TV measurement and analytics companies, Bluefin Labs and Trendrr. Twitter is the dominant channel for “second screen” interactions during TV viewing. the company has been developing ad products that target viewers of specific shows and even ad pods in real-time.

CNBC reports that Twitter has been valued by analysts at around $10 billion. Its 2013 revenue is tracking to reach $583 million.

Twitter’s could be the most anticipated IPO since Facebook’s infamous stock debut over a year and a half ago. Ironically, that social media stock only recently fully recovered from it post-IPO plummet. The share price reached $45 this week, finally exceeding the high it hit on its first day of trading in 2012.

Twitter claims more than 200 million active registered users, 60% of whom log into the service via their mobile device at least once a month.