> Re/Targeted ads require the decision to be made in milliseconds, including network transit time If they're served on page-load when a user first visits a sit

> Re/Targeted ads require the decision to be made in milliseconds, including network transit time If they're served on page-load when a user first visits a site, but I guess a significant minority are also requested+served in the middle of your newspaper article two minutes after page load, or in the middle of your Youtube video, or a refreshing sticky-footer ad, or just the next page loaded on a site.