There are several companies I am a regular customer of which I found via advertisements. If they stopped their ad spend, their revenue might not go down (I know

There are several companies I am a regular customer of which I found via advertisements. If they stopped their ad spend, their revenue might not go down (I know I would keep buying), but if they never had ads to begin with, I wouldn't have spent hundreds of dollars on their products, nor would I have recommended their products to my friends. One ad click generated several repeat customers and thousands in revenue over the span of three years - that's a good return on investment, one your analytics probably doesn't capture, and one which you certainly wouldn't notice if you stopped your ad spend. And that's the rub, isn't it? Advertising absolutely can work, but the numbers can be very deceiving, to the point that I'd bet most companies cannot say with any degree of certainty that their advertisements drives new sales, much less provide hard numbers on how effective their ad spend is.