Now that's a neat Idea, you could be a billboard when the time is right and take it down at other times... You might even get more creative and hook up your smartphone or tablet as a display on the other side with whatever wording you want.
Maybe a scrolling marquee app. Heck, you could advertise whatever you want on your display at that point.
If it then becomes a trend, one could pay people small amounts of money for becoming mobile billboards on location enabled devices.
The velcro yes, but please, please no on the other idea.
Next time I can't find a table to eat lunch at Panera the guy entrenched at a 4-person table for hours with a laptop and single coffee cup is going to try and make me read ADS? This... would be unwise.
Maybe a scrolling marquee app. Heck, you could advertise whatever you want on your display at that point.
If it then becomes a trend, one could pay people small amounts of money for becoming mobile billboards on location enabled devices.