Remember the recent story about slot machines in Canada that flashed barely noticeable jackpot images? (Konami, the maker, denied allegations saying it was a tech glitch.)
Now, 2GB writes that "Scientists at the University College London (UCL) have found the first physiological evidence that invisible subliminal images do attract the brain's attention on a subconscious level." (via Neuromarketing). There was one other recent study with similar conclusions.