The risk of advancements in technology to crack cryptography is probably another one. I don't know how severe that problem is and people say the algorithm could quickly be adapted, but if somebody cracks the algorithm I doubt that will ever become public knowledge until the harm done is really extraordinarily big. There are a couple of threads discussing the influence of quantum computing with pros and cons, but assuming that Bitcoin's algorithm might stay strong forever may also be naive to believe. [/list]