“Last Thursday I had a particularly awful iAd fill rate of 5%. This isn’t new, I’ve had problems before. Then on Friday a 0% fill rate, then on Saturday another 0% fill rate. I emailed Apple and posted a question to the company’s developer forums. Today I finally got a reply.”
Apple’s response essentially said, “…our advertisers prefer that their advertising not appear in applications that are targeted for users that are young children, since their products are not targeted at that audience.” A lot of people will decry advertising meant for children [1. Frankly, it isn’t always a good thing, so their response is warranted.], but in this case I think the reason is even simpler: kids don’t buy what advertisers are selling. Since children’t don’t click on your expensive iAd, it would be silly to keep trying.