Facebook shares have slumped again, falling as low as $29.23, just a little over a week since its initial public offering. As of 1 p.m., Facebook shares were trading at $29.39, a dramatic drop from its initial offering price of $38.

Of the top 10 largest U.S. IPOs in the past decade, according to Bloomberg, Facebook has delivered the worst performance for its first five days of trading.

There’s no doubt that Facebook’s bad debut has been disappointing for investors who had gone into the IPO with such high hopes about its possible performance. Nearly everything about the offering has failed to meet expectations, from the stock’s performance to its glitch-plagued opening hours on the Nasdaq to the reports that the debut’s underwriters may have given more information to select investors.

But even aside from the issues surrounding its IPO, the main concern about Facebook is that it can’t generate the same kind of revenue on mobile devices as it can on traditional computers. The company is moving to address this, with its acquisition of Instagram, and attempts to innovate on mobile ad formats. There were reports over the weekend and on Tuesday that the company may be trying to fix its problems with mobile revenue with acquisitions or by working on its own mobile device.

Stumbling out of the gate doesn’t necessarily spell disaster for a company — take a look at Amazon, which broke its IPO price and stayed below its initial price for months, as Benchmark Capital’s Bill Gurley noted.

But Facebook will have to move beyond the problems with its debut and show that it’s a company that knows what it’s doing and how it will move forward — something not all analysts are convinced the company can do.

Technology analyst Rob Enderle said that Facebook should be wary of doing anything as far out of their core business as making a phone.

“Facebook needs to shore up their foundation,” said Enderle in an interview with The Washington Post. The company’s revenue stream, he said, is not secure. “They haven’t locked up revenue,” Enderle said. “Until they do, wandering off is probably a mistake.”

(Washington Post Co. Chairman and Chief Executive Donald Graham is a member of Facebook’s board of directors.)

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