Advertising

Advertising ranges from brilliant to hilarious to insipid. But no matter what the content, companies are paying hundreds of billions of dollars for it every year. So I wonder, does advertising actually increase revenue? And if so, how? Does the quality of advertising really matter, or does a label that turns blue when its cold attract people as much as Mac vs. PC? And if companies are spending hundreds of billions of dollars, does advertising really generate a net profit? Most people think advertising doesn't work on them -- does it secretly, or are these companies just wasting money?