Perhaps with advancement of technology, we can have cheap, robust and energy efficient billboards on road showing advertisements. They'll probably show an HD image or a short video of a few seconds. This images can be targeted towards approaching cars. Half kilometer ahead, put a camera to profile the next lot of cars. If majority are SUVs, we can display ads of Rolex or Tag Heuer. If they are all compacts, maybe a snapdeal of discounted dinner would work. If you could identify the cars by number plates, trace it to the owners, from their lookup their facebook or google+ profile and find a common interest of next 10 cars, very likely you can display a meaningful advertisement. You'll get enough time to do so, in order of a few seconds to choose the ad, and a few more before the cars pass by. Same can happen at smaller scale. At railway station or airport, if you can find the common interest (or even interest of the guy(s) with maximum purchasing power) of the people who are sitting in the rows facing your display, ads can be tailored to them. How to identify them is a big question, though. Maybe their tickets or boarding pass will have RFID, from which we can look them up.