I came across this wonderful video of Rory Sutherland gave at TED Global last fall. It's worth watching. Here's a preview from the TED site.
Advertising adds value to a product by changing our perception, rather than the product itself. Rory Sutherland makes the daring assertion that a change in perceived value can be just as satisfying as what we consider real value -- and his conclusion has interesting consequences for how we look at life.
Image source: rush_39402