In the longer term (assuming Bitcoin survives so long) the question is whether exchanges will start to openly fractionally reserve their deposits. It might seem

In the longer term (assuming Bitcoin survives so long) the question is whether exchanges will start to openly fractionally reserve their deposits. It might seem crazy today, but if and when the exchanges develop a strong reputation for financial soundness it may be very hard for them to resist the profits from a small, very safe under-reserving. Customers are likely to go along with this because 1) after all, the BTC exchanges have a strong reputation for safety and competence! and 2) some will likely share in the profits through interest on their deposits. Of course, these small, very safe overcommitments will likely turn out to be the first step on a slippery slope, but so it goes. (I am not an expert on anything.)