Since the 1950s, advertorials and product placements emerged, and, as the internet and online commerce took hold, Amazon blazed trails by serving up book recommendations to users based on their previous purchases and online behaviors. Today, these sorts of activities-designed to deliver advertising content, online or via mobile devices, to consumers who have demonstrated their potential interest in the product or service-are known as native advertising. The practice lives on a continuum between "annoying" and "useful," depending on the perspective of the consumer. The goal for marketers is to land somewhere closer to the useful end of the spectrum.