I noticed an interesting trend: as soon as the capitalization of the crypto currency is growing at a rapid pace - immediately there are reports of "cracking exchanges by hackers." May be. it's just human greed and the owners of the exchanges only pretend that they were hacked?
Perhaps is a question of incentive. If the owner can make more profit by alleging a hack and taking everything is just a question o the weight of a possible criminal prosecution which is unlikely and difficult. Perhaps some exchanges are better than this, but the risk is there.