Here's an interesting story -- a scandal in the making, if anyone actually cared.
Background: last week Google was added to the S&P 500. Which on its own is actually neutral -- it signifies that a company is big and important, but doesn't really signal anything about expectations for the stock to go up or down.
But here's the thing: all of the S&P index funds suddenly need to have that stock represented in their holdings, so they have no choice but to buy it up. So whenever a stock gets added to the S&P 500 or any of the other big indices, it immediately has a bump up.
Apparently someone got wind of this and made a bundle just before the announcement. Put aside that Google (the company) is involved, because it may not have involved anyone at Google. And, in fact, it may not even be illegal since the S&P 500 is not a publicly traded company and thus falls outside of SEC regulations for insider trading.
But someone clearly made the system work to their advantage last week.