These are the main things I worry about with exchanges that aren't regulated by any government.  The reason I trusted Circle and still trust Coinbase (even though I don't use them) not to claim they got hacked and then run away with everything is because of government oversight and regulation.

Exchanges like Yobit?  Who the hell knows what keeps them in business.  They could easily pull a Cryptsy exit scam, and I doubt the Russian government would lift a finger to help anyone--in fact, I'm pretty sure of that.

Thus the biggest issue I have with exchanges is that of their trustworthiness, and every time I use an exchange like Yobit or one of the instant exchanges like Flyp.me, Changelly, and so on, I feel like I'm rolling the dice with my money.  Certainly if the transaction doesn't go right I've got no one to complain to.  It's crazy that 10 years after bitcoin was created we're still in the wild west where exchanges are basically unregulated.