If you just submitted an order to buy FB today, and were confident the order was executed even if at market, you may be out of luck:

NASDAQ HAS PROBLEM DELIVERING FACEBOOK TRADE EXECUTION MESSAGES

What this means is that the exchange at this point is deciding whether or not to send back late executions to all people who bought, or thought they bought. Needless to say this means that the indicated price is likely not the real price if one factors for all the latent orders, on both the bid and offer side, unless of course all those orders get cancelled, further eroding confident in the market, only this time hitting that one segment most disenchanted with the stock market - mom and pop.