I sure as hell can't come up with anything.
although fincen only care about the fiat exchanges. if..... IF there was a day they moved onto the bitcoin side of the fense by buying up the copyright/trademarks from MTGOX and then taking over armory, blockchain.info, bitcoin foundation. the first thing i would see is forcing the main software developers to add login pages to the programs. which link to personal information.
which would put a dent into bitcoin freedoms. but because fiat is government property and bitcoin is not... it wont ever happen
The entire scenario you described is impossible LOL. Nobody has anything to fear.