LinkedIn sold shares at the top of an already raised price range in its initial public offering on Wednesday, signaling that stock investors are eager to buy shares of social networking companies even if valuations are lofty.

It sold 7.84 million shares for $45 each, for a total of $352.8 million, as investors see the potential for the professional networking site to link companies with customers and job seekers. The company's shares are expected to begin trading on the New York Stock Exchange on Thursday under the symbol LNKD.

LinkedIn on Tuesday raised the expected price range of its IPO by 30 percent to $42 to $45 per share from $32 to $35.

The strong investor demand for the offering bodes well for other prominent social networking companies expected to go public in the coming months and years, including Facebook, Groupon, Twitter and Zynga.

While the companies have significantly different business models, they each tap social networks and the valuations for each are skyrocketing.

Less than a decade after it began in the living room of co-founder and ex-PayPal executive Reid Hoffman, the Mountain View, California-based company is valued at $4.25 billion.

Facebook, which is expected to go public in April 2012, was valued at $70 billion in recent sales of the company's private shares, up from $50 billion at the beginning of the year.

There is a feeding frenzy going on, said Ben Howe, chief executive of boutique investment bank America's Growth Capital.

Groupon, which brings people together for deals, has had talks with bankers about an IPO that could value it at $15 billion to $20 billion.

Yet to proponents of the value of connecting people online, the high market valuations of these companies may make sense. LinkedIn, for example, is an excellent way for companies to reach prospective customers, one venture capitalist said.

Tapping into the social network of a customer is the most efficient way for a company to find new customers, Saad Khan, a partner at venture capital firm CMEA Capital, told the Reuters Global Technology Summit in New York.

I think there's a lot of manifest destiny involved, he said. I think people are looking at the future prospects.

Both LinkedIn and Facebook allow users to create profile pages displaying a picture and details about themselves. But while Facebook tends to have more informal profile pages which may include a photo album from a recent trip, for example, LinkedIn is generally seen as the place for a professional persona. The profile pages are basically an online database of electronic resumes.

While most of the biggest social networking sites mainly make their money through online advertising or Internet services, LinkedIn actually makes more money through its offline sales force that directly solicits customers, agencies and resellers.

In 2010, 56 percent of LinkedIn's net revenue came from field sales, while 44 percent came from online sales. That puts it in competition with niche job-seeking sites and traditional recruiting firms.

At the end of the first month after its May 2003 launch, LinkedIn had 4,500 members. At the end of March, that figure was 102 million members.

The company's shares were sold on Wednesday at about 17.5 times LinkedIn's 2010 sales. By contrast, Google Inc's shares are valued at about six times 2010 sales.

LinkedIn co-founder Hoffman made about $5.2 million selling less than 1 percent of his shares in the IPO. Chief Executive Jeff Weiner made the same amount selling the same number of shares, which accounted for about 5 percent of his stockholdings.

Hoffman's remaining, post-IPO stake in the company -- 21.7 percent of the voting power -- is worth about $853 million at the IPO price. Weiner is keeping about 2.5 percent of the voting power, a stake valued at $99 million.

Other selling shareholders included Goldman Sachs & Co, which made just over $39 million on the IPO; Bain Capital Venture Integral Investors, which made $29.4 million; and The McGraw Hill Companies Inc, which made $19.6 million.

LinkedIn said it would hold its share of the proceeds -- about $217 million before paying the expenses associated with an IPO -- for its general needs and for any future acquisitions or investments, though none have been identified.

LinkedIn, which made money for common stockholders in 2010, said in its prospectus it does not expect to be profitable this year.

Our philosophy is to continue to invest for future growth, and as a result we do not expect to be profitable on a GAAP basis in 2011, the company said in reference to U.S. Generally Accepted Accounting Principles.

Underwriters on the IPO were lead by Morgan Stanley, Bank of America Merrill Lynch and JPMorgan.

(Reporting by Alina Selyukh and Clare Baldwin; Editing by Dhara Ranasinghe, Andre Grenon, Steve Orlofsky and Richard Chang)