Possible reasons:

iCloud Leak: A lot of celebs had nude selfies stolen from iCloud. (NSFW) example. (Apple PR). This story was catching fire for at least a couple of days before today though. For instance, Business Insider, dated Monday 1-Sep-14, 4.55am.

People could be jittery too; Apple has risen quite bit (~45%) this year. Perhaps people just want to get out before Sep 9?

Or it could be IFA
Basically every other device maker, showing off their latest & greatest

• Samsung Galaxy Note 4 ‘egde’ looks interesting….
• Gear S (the newest smart watch) also looks interesting…
• Sony has a smart wearable too

Wonder if we’ll see a reversal tomorrow? Any other theories?