> The fact that you can take out a loan

Why would any rational actor provide a loan denominated upon an insanely volatile "currency" like bitcoin or ethereum? The lender could loan 100 ethereum bux only to lose big time because the price of ethereum went up 10x in a week making the amount repaid worthless. Or it could go down, in which case the borrower would wind up defaulting because who would want to pay back 10x more than they were lent?

Lending requires a pretty stable currency...