1) be shutdown by non compliance/govt
2) bankrupt from mismanaging funds
3) get hacked from cheap site or incompetence
4) is unusable from bad/cheap design, system, traffic/liquidity problem
?
Well one thing that will fuck everything up is lawsuits and such. If such things become common you can kiss cryptos good bye.
There is a few good exchanges out there ATM, the issue is the lack of verity on most, let alone volume. Most of em when they see a problem they shut down to fix the problem, unlike a un-named one who lets it keep on going, while no one has a clue wtf is going on, and then blames it on the block chain...