The analysts cut their estimates because a Facebook executive who knew the business was weak told them to.
Put differently, the company basically pre-announced that its second quarter would fall short of analysts' estimates. But it only told the underwriter analysts about this.
The information about the estimate cut was then verbally conveyed to sophisticated institutional investors who were considering buying Facebook stock, but not to smaller investors.

If this allegation is correct, someone is going to prison.

EXCLUSIVE: Here's The Inside Story Of What Happened On The Facebook IPO - Business Insider