Governments operate on the theory of plausible denial ability, so no one is going to see any "proof".  You realize the CIA employs "economic hitmen" that take down whole countries, right?  Bitcoin would be joke in comparison.

You don't mess with the kings feds money and bitcoin is doing just that.
 
I think the question we should be asking is who had the most to gain by pumping and dumping (seems like "someone" really threw down a lot of fiat about 3 days before the "correction").  Also, who has the vast media influence to make the crash virtually front page news in most major publications around the world in short order?
 
It's kind-of like the cops finding no "solid proof" on a cheating, alcoholic, wife abusing husband when his wife comes up dead.