but this would be the worst case scenario for bitcoin. If Mark stole the bitcoins...... that is bad. If he gave them away because of poor programming that is also bad. But if the government of the US can come and confiscate cold wallets of exchanges because some funds sent to that exchange were from crime........ then it sets a precedent for bitcoin that is terrible. It means that exchanges could no longer trust funds sent to them and they would voluntarily start going on "coin validation" schemes which would destroy fungibility.  If it is true it is also terribly unfair because cash goes into banks all the time that is from crime in some form or another and they never go into banks and confiscate everyones money because of it.