How long before ...
Someone uses different coloured bricks to permanently put a 2D barcode on the side of a building, thus triggering 100's of smartphones into opening a web site when anyone takes a photo that has the building in the background.
Someone uses different coloured bricks to permanently put a 2D barcode on the side of a building, thus triggering 100's of smartphones into opening a web site when anyone takes a photo that has the building in the background.