I believe that actually Kevin doesn't have to give back any of it.
He purchased them in good faith. Even if the market was crashing, I would have purchased it if I saw the opportunity.
- Now, even if it is on his right to keep them, IF the money belonged to MTGOX (and not a user, but actually the main fund of MTGOX, which seems to be more plausible the more I think) then I guess that for the betterment of the economy and its stability, Kevin should give it back to MtGoX.
In exchange of the devolution, MtGox should give a compensation for the act of good faith and allow Kevin to keep the withdrawn amount - If the account was a personal one, Kevin has less obligation to give it back to the owner of it. When you make the wrong call playing poker you can't undo it, if you fucked it up, you fucked it up. Period.
But still, it would be a nice gesture, and this would be totally from Kevin's generosity, if Kevin gives back partially or totally to the previous owner. A generous compensation for this gesture would be appropriate.
BUT, Kevin has all the rights to keep it and not giving it back to anyone. He would be a total asshole by behaving like that, but it is in his right.
Now, everything depends on his will.
MtGox shouldn't rollback shit.
The least thing that MtGox can do is to compensate to all users for this scandal and for they negligence/incompetence.
The leaked userbase is embarrassing enough, and that needs a fair compensation to all of us who entrusted this site with our money, and in some cases, our life savings (doesn't matter if trusting one's savings is a unsound judgement, the point here is that our trust has been broken).
It takes decades to build trust, and only one second to break it.
Usually, one never recovers full trust with a person, but doing good deeds can help to reestablish the relationship.
I hope MtGox understands here that more than profit, trust is actually the backbone of a business.
If you don't offer a deal to keep your users happy, expect a bank run.
(Wrong thread, I wanted to post it in Kevin's thread...)