LinkedIn has finally announced its long-rumored $1 billion valuation, via a fourth round of investment led by Bain Capital. Bain, a new investor for the social network for grownups, lead a $53 million round; previous investors Sequoia, Greylock and Bessemer also kicked in. Last fall, when News Corp./LinkedIn rumors were floating around, CEO Dan Nye said the company would need "a lot more than" a billion to consider a sale.

LinkedIn is supposed to generate $100 millon this year, and breaks down the revenue stream for the NYT:

LinkedIn will get only a quarter of its projected $100 million in revenue this year from ads. (It places ads from companies like Microsoft and Southwest Airlines on profile pages.) Other moneymakers include premium subscriptions, which let users directly contact any user on the site instead of requiring an introduction from another member.

A third source of revenue is recruitment tools that companies can use to find people who may not even be actively looking for new jobs. Companies pay to search for candidates with specific skills, and each day, they get new prospects as people who fit their criteria join LinkedIn.

Video interview with Bain and other investors waxing on about deal below, but PE Hub (via PaidContent), has watched the video, so you don't have to:

In it, you'll see Jeff Glass of Bain Capital - which led the $53 million financing - David Sze of Greylock Partners, Mark Kvamme of Sequoia Capital, and David Cowan of Bessemer Venture Partners heap so much praise on LinkedIn, and on themselves for identifying this 'multibillion opportunity,' that watching the video reminded me of a late-night infomercial. (Not the pornographic kind. The kind where you end up with some crap abdominal cruncher because seemingly respectable people testified that it had given them six-pack stomachs and in your fatigued state, you believed them.)

I could only make it through the first three minutes and nine seconds of the five-minute-long production, creatively titled 'Bain Capital Ventures Joins the LinkedIn Team.' But that was long enough to hear about LinkedIn's 'genius,' 'revenue growth,' and 'future revenue growth,' as well as for Cowan to go so far as to call it a 'bargain,' and Sze to say, in earnest, that 'if you look at the user growth and the scale of the markets they're in, I think it could be a valuation that we look back and say, wow, that's one of the cheapest things those investors ever did.'