I'm sure you have already laughed about this, but I'm catching up.
So they already are telling the customers that they will never give any coins back
Just like hashlets never expire or become obsolete

But you know that Mineral is really something that is possible really, in theory at least. Running a secure and trusted exchange market is a bit different than constantly keeping hashpower needed to mine effectively on par with user demands after all.
I believe the problem lies in who consumers are putting their trust in when it comes to exchanges. Especially in this case.