Not only did the publishers lose revenue, but the sites were affected in other ways, with some not rendering as they wait for the ads to load.

It just goes to show how important this service is to some.

Google's DoubleClick ad server for publishers (DFP) went down for over an hour today, potentially costing publishers across the world millions of dollars in missed advertising revenue as Google scrambled to solve the problem. It also brought much of the web to a virtual standstill as the issue prevented pages from loading.Google's DoubleClick Service Went Down Today, Costing Publishers $1 Million Per Hour [uk.businessinsider.com]