Here’s The Inside Story Of What Happened On The Facebook IPO:
The estimate cut, moreover, was followed by three additional pieces of information that were interpreted negatively by some institutional investors:
1) The price range for the deal was increased, which made the deal even less attractive in light of the estimate cut,
2) The size of the deal was increased, which meant that more stock would be sold, and
3) Many smart institutional Facebook shareholders like Goldman Sachs decided to sell more stock on the deal—the “smart money,” in other words, was cashing out.[snip -ed]
In the meantime, it’s hard to conclude anything other than this:
In one of the biggest IPOs in history, in which a huge amount of stock was sold to small investors, privileged Wall Street insiders once again got top-notch information…and individuals got the shaft.
[Mote and more I think this company is infected with sleaze. If not, they have a lot of work to do to convince me otherwise.]
turnings :: daniel berlinger 
All true. There was one other very significant factor. Big investors know to ask for more than they really want, so if you want 20k shares, ask for 50k. They were shocked when they got what they asked for (someone I know got 5x what she wanted) and were short of capital so they had to sell. Other techs got killed that day because they were being sold to cover.
Additionally, some orders placed at 9AM were not confirmed until late in the day causing panic.