The Other Thing Advertising Does

Seth Godin had a very interesting post a few weeks ago called Do Ads Work?His point (if he'll allow me to paraphrase) was that if advertising works -- i.e., if it brings in more money than it costs -- why not spend everything you have on advertising? If you can trade one dollar for two, why not do it with all your dollars? The way Seth put it was this:So, why, precisely, do you have an ad budget?