I don't know about the spreading of rumours, but alot of funds short apple on the day of product announcements as their stock almost always goes down during the announcements.
In fairness, that sounds apocryphal. If it were really common then there would be no money in doing it because the market would have factored in days before the event the fact that the price were going to fall.
Long nicknamed the “favorite yo-yo” of daytraders and hedge fund managers – Apple’s high beta of 1.43, its prominent position in finance media and its vulnerability to rumors has made it a choice stock in short term profits, both through long and short positions
http://www.investorguide.com/article/6809/apples-aapl-mini-c...
