One of the lesser-known secrets of ad networks is how much of their traffic is international. Marketers need to understand the geographic origins of network traffic. Marketers also need to exercise some control on the split between international and domestic traffic, putting limits on the amount of international impressions the network can serve. (Unless, of course, the marketer is trying to reach international audiences, which in most cases is unlikely).

Additionally, networks typically push advertisers to allow them to optimize their campaigns for the advertiser. As a result, marketers usually have very little control over where their impressions are coming from.