I would agree with you, in the context of the fractional reserve system.
But in the case of a cryptocurrency exchange the credits and debits should be more or less equal, minus the trading fees. At least, that's how places like Mt. Gox promote themselves.
It may take longer to get your funds, if there is a "run" on the exchange, because of the flood of transactions into the system and the need to reconcile everything, but that would likely be measured in a few hours extra, not days/weeks.
But in the case of a cryptocurrency exchange the credits and debits should be more or less equal, minus the trading fees. At least, that's how places like Mt. Gox promote themselves.
It may take longer to get your funds, if there is a "run" on the exchange, because of the flood of transactions into the system and the need to reconcile everything, but that would likely be measured in a few hours extra, not days/weeks.