I read a financial newspaper report earlier today predicting good results for Tesla for its quarterly earnings report today, and thus a likely continued strong performance of Tesla stock. Seeing the headline of the article kindly submitted here prompted me to read the fine article, of course, and also to check for other news stories from later hours of today about Tesla.
In approximate chronological order:
"Tesla Motors stock slides despite delivering 5,500 cars in third quarter"
http://www.mercurynews.com/business/ci_24460515/tesla-motors...
"Tesla Beats Expectations On Record Sales, Investors Decide To Sell Anyway"
http://www.forbes.com/sites/markrogowsky/2013/11/05/live-tes...
"Tesla loses $38 million; adjusted results beat forecast"
http://www.usatoday.com/story/money/cars/2013/11/05/tesla-ea...
"Tesla outlook, deliveries fall short amid capacity constraints"
http://www.reuters.com/article/2013/11/06/us-autos-tesla-idU...
So a lot of investors saw news about the same earnings report, but some considered differing additional sources of information, or simply interpreted the same report differently. Different investors have differing investment goals, so it's not completely surprising that the same news can prompt some investors to sell while others hold and a few even buy.
It will probably take a few more days to be sure what interpretation of Tesla's news is most persuasive to the largest number of investors. (Disclosure: I do not own stock in Tesla nor do I own stock in any other company. My son the hacker has an investment portfolio, but I have no idea what is in it.)