Facebook opens at $42.99 a share*

A solid but not spectacular pop from the $38-a-share offering price. Very hard to wrap your arms around this one, given the size and hype (keep in mind that they're moving $18 billion worth of stock). The general consensus is that Facebook is overvalued, but many were saying the same thing about Google some years back. So who knows?

*Update: A little before 9, Facebook shares were sliding back to near the offering price. It's at $38.55.

*Could the underwriters be propping up the stock at $38? That's the chatter.

*Amazing stat: Facebook traded 82 million shares in its first 30 seconds of trading, says CNBC.

*Quite a few trading-related problems after the opening, the WSJ reports. And yes, underwriters did step in to support shares at $38.

*Why wasn't there much of a pop after Facebook began trading? From Business Insider:

A theory from a source close to FB's IPO bankers: The volume that caused NASDAQ to delay the IPO for more than a half hour, also prevented Nasdaq from informing big bank trading desks whether or not their trades on Facebook had gone through. This left trading desks in a position where "you don't know whether you bought it, and you think you did at $42 but you're not sure," says our source. That "uncertainty" combined with a huge amount of stock supply led to a "wave" the brought the stock back down to $38.

*A little before 10 a.m., stock is at $41.11.