Susanne had a great PaD shot of flags a few days ago - and several people commented that they recognized the Maryland flag even though they didn't live there.
Well, this is why. I live in Maryland and in many of my images, I include a very, very subtle subliminal message showing the Maryland state flag. Like this photo of a purple Peep. The flag isn't obvious when you first view the photo, but the longer you stare at the image of Purple Peep, the more the Maryland flag will be implanted in your mind.
Susanne's PaD shot: http://www.pbase.com/susanne_medic/image/43222006