There is also nothing preventing exchanges from dumping "your" BTC for cash from a pure technical standpoint. Because technically, all you have is the promise

There is also nothing preventing exchanges from dumping "your" BTC for cash from a pure technical standpoint. Because technically, all you have is the promise of the exchange to transfer you the right amount of BTC out of your account whenever you request them, or the same market value in another (supported) crypto/fiat currency. This is not only a pinky-swear promise but one protected by some laws and contracts. But it is very questionable to me if there is (or should be) any obligation for any exchange to pay you any amount of BCC that magically appeared overnight.