1. For a bank run on an actual bank, it is known that a bank doesn't keep all your assets on hand - they are loaned out, which is (largely) what allows you to earn interest. So it is known that if everyone tries to withdraw at the same time that there won't be enough money.
2. For an exchange/brokerage, your money/assets are explicitly NOT supposed to be lent out without your permission. So, in theory, if everyone asked for their assets all at once, the assets should be there.
But we already have a whole bunch of examples of (2) where the funds ended up in all kinds of places where they should not have been.
An exchange can hedge vs excess buy orders by buying the underlying, but how do they hedge vs excess sells?
I've been trying to figure out how to short BNB, and perps feel pretty much as risky as trying to do it on binance itself.
In case of regular futures, price discovery is aided by the fact that the futures eventually settle to either the underlying or its cash value at a specific point. In perpetual futures, price discovery is aided by "funding fees," which are periodic cash transfers from the side that is contributing to the price discrepancy between the future and the spot to the opposite side. E.g., if perp is below the spot, the short holders will periodically be charged the funding fee, which will go to the long holders, to encourage the shorts to buy/get the price closer to spot, etc.
The lure of those balances is invariably too great to resist.
I think the folks at JP, etrade, and all of the other regulated exchanges would object to that characterization.
Time and again we find that exchanges have been dipping in and using money that wasn't theirs in ways that would never fly in a regulated environment.
They are leveraging and borrowing from the customer funds with abandon, just like a bank but without the associated regulatory oversight and rulebooks.