Virtuality
Virtual money stolen from virtual database and virtually no chance of getting anything back....
It's not easy to transport tonnes of gold (thinking Fort Knox here), but a couple of bytes of data is easily within the means of the scrawniest hacker.
As much as I don't trust the banks with real money, which is what actually comes out of the distributor, I have a hard time in trusting anyone with Bitcoins and especially their ability to suddenly become vapor...
Outside of the Black Market Rascals I have a hard time understanding how anyone can trust the world of the Bitcoin Magiciens. ( Yeah, I know I am just being cynical but .....)