Consider that people freely decided to keep money in MtGox. The whole currency is unaffected. But when your central bank decides something (e.g. to issue more c

Consider that people freely decided to keep money in MtGox. The whole currency is unaffected. But when your central bank decides something (e.g. to issue more currency or do a haircut), then suddenly all banks and all holders are affected. Example of MtGox is an example why Bitcoin is important and actually works as promised: one company misbehaves, others not affected.