The idea that you put your money on an exchange is a contract of trust, Mt Gox betrayed that trust by intentional deception. Other exchanges that had problems (hacked, regulated out of business etc.) "most" were open and honest when it happened. Coinedup was a good example of how not to screw over your customers.

Closing an exchange then keeping your customers money or holding it ransom or any variation of that without a really good and verifiable justification is theft.
The amount does not matter its the principal that does..

The reason they gave some customers for not returning funds was that it was allot of work (?)
They then close the site and demand payment to get your funds back?