I thought one of the advantages of the block chain was that all transactions are logged. So even if the millions from ransomware were to be divided up between thousands of different bitcoin wallets, as soon as they try and cash one out with a coin exchange at that point they will need to reveal their real identity to get in back to fiat currency.
I can't see how they can be actually benefiting in the real world for these ransonware scams, as what is the point in having millions of dollars in bitcoin if you can't actually spend it on anything tangible or are there some dodgy exchanges that will payout cash with no ID and no questions asked?