As we all know, few days back on 1st august Bitcoin Forked into Bitcoin Cash and only a few exchanges supported it.
People were advised to keep their cash off Exchanges or in any wallet where they own the private keys ! Sadly a Majority failed to move funds as they had no Idea how to do so or due to "network congestion"
What people failed to realize that this was a big opportunity lost to gain money ! And somone else may have made profit from their BTC. Lets take an example to explain this situation :
Suppose you had just 2 bitcoin and you kept 1 on a paper wallet and another on Coinbase. Of the coin you kept on paper wallet you are free to calme 1 bitcoin cash (which was around 400$) now the other one was at coinbase, you don't own private keys to it. But coinbase does !
So if they wanted they could use the private key assigned to you to claim your share of Bitcoin Cash and use it for themselves.
And there is nothing you can do to stop them. Even if you wanted to. Because you have no Idea what your private key is.
Now think of the number of users who did not move their BTC to get their share of BTC Cash...