You can believe: btc-e, bittrex, cryptsy.
Well i wouldn't so sure about believing these exchanges.
For example we can see here that there are many accusation about cryptsy.
Where they block/disable their users accounts, isn't this the worst situation about trusting or not the exchanges!
It is and you just can't, if you must use one then just go there do your thing and get out and hope that nothing happens for the time you're there, as short as it might be. I don't truly believe the exchanges who were so called got "hacked" in the past, I think it was all a cover up, it was a perfect crime, wait for the moment when there are a lot of public funds and then bam! go offline abruptly with a story that one of our employees did this this.. and we were hacked. And since there are no legal tie ups, sell the bitcoins slowly and then start again.
That's a hell lot of accusation, we know Gox was an inside job like you are saying, but there are also legitimate exchanges that closed entirely due to external factors. Look at MintPal, if it hasn't been bought by the Moolah scammer, it would have been a much more established exchange than Bittrex.
