The fact that the feds are making them erase all the files goes to show that they dont know what they are doing
The fact that you wrote that shows that you don't have a clue as to what is happening in this case.
People, MU was a front end service, they actually rented out data space on 3rd party server farms. Please, for the love of anything you hold dear, let that sentence sink in. Those 3rd parties are holding your data and their contract was with MU, not the end users.
If MU doesn't pay them, then they have every right to free up that space so they can rent it out to another entity, unless whatever judicial entity that has jurisdiction over the 3rd tells them not to (which hasn't happened).
So the US gov is not deleting anything, they are simply relaying the info that the 3rd parties are saying they are going to do. The end users have no legal recourse with the 3rd parties either as they were interacting with MU, there were no contracts in place between them and the 3rd party vendors.
Most likely the 3rd parties wouldn't even be able to give back the info if they wanted to because they wouldn't be able to authenticate the end user without MU front end.
You want to blame someone, blame MU for their poor business practices that led to this, blame yourself for not making a copy or for using MU without really knowing what you were getting yourself into.
It took me all of 10 minutes way back when to realize that MU wasn't the service you want to use, told a few friends too, simply because they specifically did not physically store your data. If, for whatever reason this happened to say...Google, you'd have a decent chance of getting your data back at some point in time. This is because they themselves store the data. Should the gov freeze them, there's no reason for the data to get erased, unlike a 3rd party vendor who would need to open that space up for another client in order to stay in business.