On: Single Tweet Sends Apple Shares Soaring

Not necessarily refuting what you're saying, but here's an interesting take on "purely by chance" from Buffett, by analogy of coin flipping and getting a run of heads: http://www.tilsonfunds.com/superinvestors.html

That's a great article, thanks. I actually had the coin example in mind when I wrote the comment, but was too busy to write out the full argument!