Advertising opportunity?

The flight from San Francisco to Tokyo was about 10 hours, and so I had lots to think and wonder about business (and other stuff, of course.)

Why no one puts any advertisement inside the plane, where people just sit for hours?

Later I found out that a few carriers such as Spirit Airlines actually do place advertisements on overhead compartment covers and tray tables: http://www.wired.com/autopia/2008/10/airplanes-becom/

These airlines that do not like to force the passengers to stare at a logo still puts bunch of ads on their in-flight magazines.

Japanese version of this article is here.