I think in general it does not bring the return it advertises. Buying adspace directly from a website that is known to be a fair dealer would be different, or trading adspace here, for adspace there. But radio or TV or print advertising, where it is always guesswork how many people are reached and how many of them buy. Those numbers are always exagerrated by the seller, and therefore prices are inflated. These forms of advertising are typically only a good return for the established player who gains additional value (aside from purchases driven directly by the ad), such as helping to maintain market dominance, or control/ influence over the network/station/paper/publisher (Pfizer), or brand saturation (liberty, liberty, liberty). For an upstart competitor entering the market, falls on deaf ears IMO. Any service that provides 'impressions' in exchange for 'cost per clicks,' is as gameable as youtube views are. Buying podcast mentions is guesswork, but probably pretty good in this space, assuming you go directly with the bitcoin friendly podcasters, and not to some service.