Let's not forget that prior to Thursday May 17, the IPO price range was announced to be at $28 to $35 . Not only that, but they also increased the size of the IPO by 25%, as I recall. This is essentially the same as noted by the Washington Post:
"Facebook originally set a price range of $28 to $35 for its IPO, which would have valued the company at $95 billion at the high end. Last Tuesday, though, it increased the price range to $34 to $38 per share, valuing the company at as much as $104 billion.
"Then, responding to extraordinary demand from prospective investors, the company announced on Wednesday that it would add 84 million shares to the offering."
So Morgan Stanley got caught up in their own hyping up of Facebook, ups the size and price of the IPO, and now the price drops back to where they initially priced it (for a smaller number of shares). That's not the best outcome, but it's not as if it means Facebook will go under.
Now if the price keeps falling, that's another story, but at this point, it seems a lot of people are buying on hype, so it's no surprise that some people are going to have a bad time.
 Facebook IPO: The art of pricing the right pop