LinkedIn Corp.’s shares more than doubled in their public trading debut on Thursday, evoking memories of the investor love affair with Internet stocks during the dot-com boom of the late 1990s.

Shares of the online professional social networking company soared as much as 171 percent, or $76.97, to $121.97 in afternoon trading on the New York Stock Exchange — far exceeding the $45 initial public offering price.

The stampede brings the valuation of LinkedIn, which less than a decade ago was no more than an ambitious idea and a computer in one man’s living room, to as high as $11 billion, depending on the stock price at the moment.

LinkedIn is the first prominent U.S. social networking firm to publicly test just how hungry investors are for anything social media-related on the Web such as Facebook, Groupon and Zynga.

Millionaire in one day

LinkedIn Chief Executive Jeff Weiner — a newly minted millionaire — shrugged off the trading craze or even worries that the pricing underestimated the appetite for the stock.

“Speaking for myself, personally I’m not even thinking twice about where the price is today and leaving money on the table or even anything remotely along those lines,” he said, adding that the stock “will take care of itself.”

Weiner, who sold about 5 percent of his holdings, made $5.2 million on the IPO.

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