LinkedIn has hired investment bank Allen & Co. to help it raise a round of funding that would set the company's value at $1 billion. Last fall, LinkedIn CEO Dan Nye said the company would sell itself outright only for a "a lot more" than $1 billion. In January, he told a reporter "an IPO is by far and away the most likely outcome." But that was January. While the public markets are rough, private equity remains flush, making it a safer bet for raising money. We hear LinkedIn takes a tidy profit, selling advertisers on its 41-year-old, six-figure-making average user and earning $45 CPMs on ads in the process.