How about an ethereum smart contract that gives back your money unless the owner releases the key used to encrypt your files (which may be possible to verify in the contract)
That would possibly work in the case of locked files, but not in the case in the submission, where it was about the public release of files. There's no way to ensure they blackmailer didn't keep a copy, and won't threaten again or release anyway.
Also, I'm not familiar enough with ethereum to know whether there are downsides to using it, such as it leaving a trail until laundered (like bitcoin).
Also, I'm not familiar enough with ethereum to know whether there are downsides to using it, such as it leaving a trail until laundered (like bitcoin).