Fed oversight is likely to increase dramatically.
You of course have the stuff mentioned, ransom attacks demanding payment in crypto and crypto enabling online black markets.
You also have tax issues. The dollar is the only legal tender in the United States; everything else is an asset/property. With crypto: if you mine crypto, you immediately owe taxes on whatever you mine. If you buy crypto for $10, then use it when it's worth $15, then you owe taxes on the realized value of it. If you run a business and accept crypto, then your accounting also has to include the fair market value of the crypto at the time of the transaction (and of course calculate any applicable sales tax). That's money the feds will come after at some point (especially from small time investors, since that's their favorite target for enforcement).