Is there a study on the (in)effectiveness of online ad campaigns? Is it or is it not a bubble that drives all this ad publisher to the ad platforms instead of buying ads more directly? I don't know the prices but I can bet buying an ad directly from a vlogger is cheaper and more effective than any ad platform out there. Is it really the dumbness of ad publishers that keep this system alive or is it me that I'm really ignorant when it comes to the economy of internet?