Whilst I'm not convinced by the IAB's arguments here, it's worth noting that not all sites - indeed, most sites - aren't as easy to target as the examples you g

Whilst I'm not convinced by the IAB's arguments here, it's worth noting that not all sites - indeed, most sites - aren't as easy to target as the examples you give. Speaking as someone who buys a fair bit of advertising, there are thousands of sites in the inventory of most RTB sellers which I'll just skip over unless their inventory is really cheap, because it's very hard to figure out a single product that most of the site's readership would use. (Example site - Photobucket. What ads would obviously make money on there?) Also, for quite a few sites where the core demographic does have some obvious interests, there aren't that many well-paying advertisers for that demo. Retargeting and similar tracking-based advertising systems help fill in the gaps when the core advertisers aren't buying all the inventory.