I think some panic could occur if satoshi would start moving his treasure (it's over million coins and if decide to sell it asap the price drop would be significant IMO).

As of the hack, search about "majority attack" (or 51% attack) .. this requires attacker to controll more than 50% of total hashrate. Important to note .. if the attacker controls such hashrate, it means he invested a lot of money and much more likely he will just keep mining ( to get his investment back ) rather than attacking the network and risking it will collapse.