The only reasonably accurate targeting I've ever run into is the occasional ad for something I just browsed on Amazon. I've never clicked on an internet ad. Youtube advertising might as well be targeted to an alien race. What in the hell keeps this whole business afloat at it's current level? Am I being programmed to buy that mechanic's vise because they threw up an after-the-browse ad?
No doubt there's some sort of backend telemetry that proves the value of all this trouble, but I just don't see it. Maybe the emperor really is nekkid.
edit: It may well be that the real marketing genius in the advertising industry is not it's value in increasing sales, whether it's old school print media/OTA/tradeshows or the newfangled spying-on-you internet variety, but in convincing it's customers of advertising's value. Anything beyond pushing you up a search engine's ranking strikes me as a sketchy proposition.