That may or may not be true. Every search has a stimulus. Most people don't wake up with a craving for widgets and go straight to google. Something that they encounter offline or online leads them to believe that they need to buy widgets. The problem with traditional display advertising is that it takes a shotgun approach...the goal is to show people as many banner ads as possible in the hope that you can make an impression with one of them (and prompt someone to search for your product). Someone with the amount of data that amazon or facebook has could do a lot to improve the general quality of those ads.