Today's negative headlines included "SVP sell 12k shares", "new Kindle HDX to challenge iPad", and "Samsung beats Apple to a curved screen" -- or words to that effect.
Couple that with general market that has retreated for the last 5-days, and I see some compelling reason that short sentiment won today.
Ah, but! The good news that has been released and the good news in the days/weeks ahead will prevail. As I've seen several posters mention, if you've been wanting to add to your position, now is a great time to do it. Great earnings soon to be released, China Mobil deals soon to be announced, as well as share buybacks and, possible, dividend increases. Couple that with Apples new iPad rollout and TV/smartwatch announcements, and the competition DOESN'T STAND A CHANCE in the not-too-distant future.