Another thing is the bug that the uppers posts already mention, talking about dumping Satoshi holds a million bitcoins, that could mean he is also a threat at that context, right?
We think, based on some patterns evident in the ExtraNonce field of early blocks, that Satoshi mined around 1 million bitcoin, but we have no way of knowing that for sure unless he returns and signs a message from all the addresses he controls or something similar. If he were to try to sell all one million coins at once, then undoubtedly the price would crash, but that is based on the assumptions that he is still alive, he still has access to all his private keys, he did indeed mine one million coins, and he would want to make his own coins worthless by dumping the price so quickly. What's far more a threat is price volatility and the low utility of the coin. It's just not useful as a currency.
Oh damn. Here's me using bitcoin as a currency on almost a daily basis, but just finding out it's not useful as a currency! 
Why do you say it is not useful as a currency? I can spend it for goods and services with better privacy, faster finality, more security, and lower fees, than I can with credit cards or PayPal. Just because there is not widespread adoption yet does not make it a bad currency.