The particular ones I remember were Bus shelter ads in the UK about a year ago. I think I might have made a mistake and be thinking of ads for a Samsung phone. From a distance, with the specific app grid layout and general colour distribution in the image they looked a lot like iPhones. See the image in this article: http://mynokiablog.com/2011/04/19/itc-staff-recommends-sidin... PS I haven't read the article, just found the image on google image search.