My guess is that if your country taxes cryptocurrency mining (Bitcoin Mining for example), then whatever the tax law says about that is an apt comparison for generating SP/SBD via blogging. It's an aesthetic difference, nothing more.

Proof of Work = Proof of Brain

With one you are using a pickaxe, with the other, a pen.

The real challenge is in calculating all the correct values for each small author and curation reward over the course of a year. But I imagine some intrepid young programmer could easily write a program to calculate that for people.