Ahead of the curve=>Next step: Confiscation.

[MrDannimal]

No, he's saying that you don't need to keep enough cash on hand to cover ever dollar held on deposit all the time. That's overkill, because the odds that every account holder will withdraw every dollar in their account on the same day (barring an event you could react to) is effectively 0.

If you look at a bank, and totalled the amount of money as "available balance" for all customer accounts, then looked at all available cash on hand (with which they could fulfil withdrawl requests), you'd see that the former is far larger than the latter.

If you held all of the cash you were given as deposits, you'd never be able to use that cash to generate profit. A bank takes deposits from people, and uses that money to provide loans to other people. They charge more interest on loans than they on deposits, and pocket the difference (among other things).

Guaranteeing a deposit can be withdrawn to each customer assumes that not every customer will want to do that at the same time.