A conference speaker recently suggested that your media buy should reflect the amount of time consumers spend with various media. His graph showed lots of time spent online and far less with print media. His conclusion: spend four or five times as much on digital ads as on print. Not so fast. First, we engage differently with different media. Relaxing with a favorite magazine is different from browsing online. His chart left out mail (traditional and e-mail), which may consume less time but enjoy much deeper engagement. And he glossed over the fact that his chart showed more time spent with TV (not his medium) than digital (his medium). The moral of the story? Take expertise with a grain of salt. And consider how your prospects engage with media before you buy.