What about a legal agreement with the users that the information will be deleted before a bankruptcy is filed and if they fail to deliver, then the users are owed so much for failure to deliver on the contract (and this debt is created in such a way it takes priority over other debt). Make the debt big enough that anyone owed money for a reason other than this deal (so investors and such) would see a greater payout by deleting the information and selling the other assets with their normal claim to its worth than by attempting to sell the customer data and split the proceeds with all the users.

Also make it legally solid enough that even if there was a lawsuit, the cost of the lawsuit would be higher than the worth of the data.