Default risk. The price for a bitcoin that is currently held by Mt.Gox factors in the market's expectation that said bitcoin will be able to be redeemed from Mt

Default risk. The price for a bitcoin that is currently held by Mt.Gox factors in the market's expectation that said bitcoin will be able to be redeemed from Mt.Gox. Analogous to why your bank charges you a higher interest rate on a loan if you have a poor credit score, to compensate them for the perceived risk that you fail to repay the loan.