I suspect that this would be classed as subliminal advertising here In Australia, which is banned by the television code of practice:
"1.8.4 use or involve any technique which attempts to convey information to the viewer by transmitting messages below or near the threshold of normal awareness."
An interesting subliminal advertising case cropped up a few years back: http://www.abc.net.au/mediawatch/transcripts/s2082405.htm