Here's the scenario: Engadget, the popular tech website, gets an email claiming the Apple iPhone would be delayed a few months. They immediately fact-checked the story... oh nevermind, they took the story and ran with it on the front page. Only later would they learn that the email was a hoax, and the story was removed.

No harm, no foul, right? Well, not exactly. Engadget is read by many industry insiders and investors. It seems that after the story ran, some very big investors, likely hedge fund managers, dumped Apple stock, causing a brief dip in the stock price. The tip from nearly $108 per share to about $103.50 is the equivalent of $4 billion in market share wiped off the table.

While the stock price did recover, many investors were likely hurt by the dip. Some people have their brokers (or software acting like a broker) sell their stock if it dips to a certain point. They do this to avoid being hurt in a big crash. Those people may have come back from lunch today and checked their stock portfolios only to find that their Apple shares were gone, sold for several dollars less than the current market price.
Engadget Knocks $4 billion off Apple Market Cap on Bogus iPhone email