Actually, he's not being charged with money laundering, but conspiracy to commit money laundering. This means he is not alleged to commit money laundering himself, but helped others do it. He logically cannot have committed money laundering (disguising the illegal origin of money), as the illegal trades on Silk Road happened after BitInstant/Charlie sold Bitcoins to BTCking. What we have here is called "reverse money laundering", when "clean" money is used to commit crimes.

That being said, I regrettably agree with Goat that it does not look good for Charlie. Even though it does not look like he committed money laundering, that's not enough to get him off the hook.