Apple's shares had a great runup until the announcement and speculators are probably getting out in droves now, cashing in on handsome profit margins, especially if they bought options a month or so ago.
The fruit company is with the largest market cap, and just rumors about the NASDAQ rebalancing its weight in the index brought the shares down recently. Not to mention how many investors - from pension to hedge funds - are loaded on Apple shares, so any significant movement down always brings a big kerfuffle with it.
A similar drop occurred after the iPhone 4S announcement, but Apple proved the underwhelmed investors wrong by still selling a record amount of its new phones in the next months.
source: GoogleFinance
