The ‘like’ was unassuming. Few anticipated that a miniature, good-willed icon of a thumbs-up could dictate corporate and cognitive wellbeing. At its best, the like has been massively generative to individual and industry alike. It’s turned people into brands, spawning influencer culture, and has reshaped global marketing.

But the like isn’t always at its best. People have died chasing them (think selfies on railroad tracks) and taken their lives for not...