This isn't your grandfather's stock market let alone your fathers.
Now a days, even the big boy stocks like Apple can and will get moved around at a moments notice.
Case in point, some activist investor, say a Karl or a Jimmy bob, but in this case a Carl, hints to the social networks that he'll tell the world his next investment idea.
Next thing you know he gets an audience or says he had one with the CEO of such a company, he says something about taking a huge position in said company, hints that the CEO should buy back a lot of the companies stock.
POOF, 20 billion dollar swing in market cap.
I am no expert, but this seems crazy and distressing.