This egregious seizure is just further proof that the Fourth Amendment is pretty much dead. Any kind of forfeiture without probable cause should be a Fourth Amendment violation but yet civil asset forfeiture (the most egregious form of Fourth Amendment violation) remains legal.
Probably the worst thing about this case is that the government has been caught in a lie and isn't backing down and they want to keep the contents. Any "evidence" gleaned from these contents should be absolutely inadmissible without prior and specific probable cause. There should be no allowance for "there's no reason why legitimate customers would use USPV instead of a bank".
Lots of people distrust banks. Not using a bank is not evidence of a crime let alone probable cause.
I really hope the FBI and the US attorney get their rear ends handed to them over this but I have doubts they ever will.