Just how much user-generated content (UGC) is out there right now? As of May 2019, more than 500 hours of video were uploaded to YouTube every minute; more than a billion hours of all those videos get watched every day. Facebook has more than 2.7 billion monthly active users, the vast majority of whom post and share family pics, jokes and memes.

There’s probably no way to measure all the content going up every second of every day on Amazon reviews, question-answer databases,...