US social networking website LinkedIn has made a strong debut on Nasdaq, with stocks more than doubling from their IPO on the first day of trading. But critics worry investors are overlooking a key point.

 

Cheers and applause marked the opening trade as LinkedIn makes a very successful debut on the New York Stock Exchange.

Excitement on the trading floor was palpable as the stock opened at $83 a share, quickly topping $100.

That's more than double the $45 a share set in the initial public offering late Wednesday.

LinkedIn raised nearly $353 million, valuing the company at more than $4 billion.

But frenzy over the professional social media website immediately drew comparisons to the dot-com bubble, causing concern investors are once again overlooking one key metric - profits.