One reason I doubt that voice devices will replace smart phones is that the phones are mobile. This makes them inherently more useful to consumers. It also lets companies like Netmining track people as they move about. This, in turn, enables deals like the one that Netmining just announced with digital out-of-home media agency Vistar Media, to target out-of-home ads more precisely. That’s a good thing for marketers, although consumers have little reason to care.