I was reading about different brain waves.  You have Beta, Alpha, Theta, and Delta brain waves.  the most interesting of all (in my opinion) is Theta.  Your brain reaches this frequency level while driving, watching television, day dreaming, or sleeping.  While driving you have billboards.  While watching television you have commercials.  While day dreaming there could be the posibility that you may flip through a magazine not even paying attention to whats going on, but your brain registers a handful of ads within minutes.

So what do you suppose we dream about when we don't remember our dreams all too well, or even if we do for that matter.  Our dreams our influenced by the thousands of ads our Theta FM brain absorbs.  Which would then explain why we may impulse buy in moments of boredom or we wake up craving a specific food item.