-By Adweek Staff

BOSTON LinkedIn, the professional networking site, said it has raised $53 million from investors that places the company's overall estimated valuation at more than $1 billion.

Bain Capital Ventures led the round -- the fourth for LinkedIn -- with existing company investors Sequoia Capital, Bessemer Venture Partners and Greylock Partners also supplying funds.

David Cowan of Bessemer, in a transcript of remarks provided by LinkedIn, said:
"Compared to most startups, LinkedIn's valuation is very high, but compared to what we think LinkedIn's future valuations will be, it's a bargain."

Mountain View, Calif.-based LinkedIn said it has raised $80 million overall in investment capital. The network has close to 25 million members, a number expected to surpass 30 million by year's end.

By way of comparison, social networking leader MySpace, a unit of News Corp., has 110 million members and Facebook has 70 million -- but those services are more social- and entertainment-oriented than LinkedIn. (Facebook late last year was valued at $15 billion following a $240 million investment by software giant Microsoft.)

"This significant investment is indicative of the confidence shared by our investors in our business model and our long-term growth strategy," said LinkedIn CEO Dan Nye on the company's blog.

"This additional funding will give us even more flexibility to execute on our vision for millions of professionals to increase their effectiveness by using LinkedIn to build relationships and exchange knowledge, opportunities and advice," Nye said.

In terms of advertising, LinkedIn offers an older, more upscale and professional-leaning demographic than the more youth-skewed nets like MySpace and Facebook.

"We're totally committed to the advertising business," a LinkedIn rep said. "We offer advertisers the ability to connect with an audience of 23 million affluent, influential and ambitious professionals in a very clean, well-lit and clutter-free environment."

LinkedIn's average user is 41 years old, makes almost $110,000 per year and is seriously engaged in business networking.

Precision targeting is also a key selling point, with LinkedIn noting that it can deliver not just groups of friends and associates, but executives and highly engaged pros in specific niches like IT, small business, finance and sales.

"We're exploring a number of innovative advertising products that will allow marketers to deeply connect with our members in a very relevant manner," the rep said.