Almost every social network of note had an early signature proof of work hurdle. For Facebook it was posting some witty text-based status update. For Instagram, it was posting an interesting square photo. For Vine, an entertaining 6-second video. For Twitter, it was writing an amusing bit of text of 140 characters or fewer. Pinterest? Pinning a compelling photo. You can likely derive the proof of work for other networks like Quora and Reddit and Twitch and so on. Successful social networks don't pose trick questions at the start, it’s usually clear what they want from you.
And this is likely the reason that the longer form blogs never went out of style in areas of higher education where people are still posting long form content. This "proof of work" is something they ultimately end up using in other areas.
Jessifer example of three part post written for a journal that was later put back into long form for publication.