I think users should not leave BTC at exchanges. In such cases, you will have control over both coins in case a hard fork occurs. You also minimize the risk of losing money if exchanges get hacked.
I am not too much understanding about this Hard Fork issue but what are the possibility of loss for a btc user when this happens ? ; I just want to know to inform myself more about the situation as i have no clue what tension going on about this Hard Fork thing ..