I think what many of us question is whether nor not those same $0.5 trillion would be generated by contextual ads. There's no doubt that ads work, but we really don't know to what extend.
E.g. if I'm on a pages looking at watches, should I get ads for watches, or would it be better to show ads for the washing machine I was looking up last night? Google, the search engine, clearly thinks it's better to show ads relevant to my search term, but they are also in a special position that's not applicable to a news website.
People working in the field has also previously commented, here on HN, that the ad networks are basically hustling the advertisers, selling them ad space / users that they know will perform badly, to move more "inventory". That generates economical activity, but does that benefit anyone beyond the ad networks?
E.g. if I'm on a pages looking at watches, should I get ads for watches, or would it be better to show ads for the washing machine I was looking up last night? Google, the search engine, clearly thinks it's better to show ads relevant to my search term, but they are also in a special position that's not applicable to a news website.
People working in the field has also previously commented, here on HN, that the ad networks are basically hustling the advertisers, selling them ad space / users that they know will perform badly, to move more "inventory". That generates economical activity, but does that benefit anyone beyond the ad networks?