Rod Harris, president and CEO of TruckAds, coins the term "Soft Target Advertising". Briefly, he describes this as a form on non-invasive advertising. Those targeted are not forced to view the ad. It is just there for them to se if they choose to see it. A sort of polite advertising if you will. If there is such a thing.
Most forms of out of home advertising would fall into this category. Of course, being the president of TruckAds, truckside advertising is, of course the best form of "soft target advertising" :-)