I have never used Magic the Gathering Online Exchange, but I feel the same as you.
I have an idea to start an exchange, find a person with a lot of bitcoins, then write a simple program to save his password in clear text.
Access his account, sell all the coins to crash the market and then freeze/rollback the market exactly the way it I want it.
I would keep the coins of every single person that cannot prove they own their account, or if I simply don't like them.
I would make up any story I want. If parts are shown to be questionable, who cares? I would give most people their coins back, and they will still support me.
I would never do it of course, but I feel it has already been done.