Sometimes I use my cellphone to actually call someone.

         When I give students my first lecture on media, the last item I cover is mobile advertising. It should really be the first.

         Bloomberg reports that Facebook has announced its next billion users will be added mainly on mobile devices rather than computers. "By providing this opportunity on mobile devices, we can make the pie bigger and much more quickly," said Vaughan Smith, Facebook's director of corporate development.

         Facebook now has 800 million users, but the shift is to smart phones and tablets, Bloomberg says.

         I see it every day in my classes, in public transportation, on the street. It seems like every minute people aren't doing anything, or even when they are, they reach for their cellphones.

        Students tell me who's going to be late to class, who's home ill. If we need a fact checked in class, someone always gets the answer on her cellphone. It's always distracting, though, when texts come in. Which they seem to do in a steady stream.

       That's here in the U.S. In India and Asia, there are less computers, more cellphones.

        Cellphone advertising advocates are making extravagant claims. They say that mobile ads are better than print because they can dominate the screen. But look how small the screens are. Who needs a tiny Tide commercial? These advocates also say people are more likely to act on cellphone ads. In many cases, I'm sure that's true, when the cellphone ad answers an immediate need.

       I even predict that the time will come when we get cellphone service free, like radio and local television, because advertisers will be footing the bill.

        As marketers, we have to figure out the best roles for mobile in the marketing mix. It great for sales promotion, but what about its role in brand-building? Is there one?

        Once we get beyond the tech magic we can do on cellphones, what's the ideal content? Is it news, information, relationships, community service and/or entertainment? Much research has yet to be done.

        Finally, how will we ultimately react to this rush to mobile advertising? Will we continue to be amused, or will people become angry, annoyed, grateful, dependent or disgusted? It's important we keep watching.