Lesson #1:
NEVER leave any funds on ANY exchange...
You can't ignore the fast moving nature of crypto and the slow moving nature of BTC and other coins for contributing to people feeling they need to keep funds on tap inside exchanges. They know they shouldn't do it, but its evidently a risk many are prepared to take.
DRK will introduce instant transactions which should make it feasible for traders to keep their coins in their own control and move them in and out of exchanges on demand.
https://darkcointalk.org/threads/paper-transaction-locking-and-masternode-consensus.2418/