DUSTIN OTTON took the bait. The 28-year-old barista was idly scrolling through Instagram when a pair of pastel-colored Asics sneakers (a collaboration with Boston boutique Bodega) caught his eye. The sneaker’s sunset palette and speckled sole leapt off the screen, and Mr. Otton’s scrolling thumb went into park. He bought the shoes.
For Julian De Sevilla, 24, a social media manager in Tallahassee, Fla., it was an arresting yellow hoodie from John Elliott that gave him pause. The instagram post in question actually showed an...