For a long time ask.com had one of the only Google ad feeds allowing them to programatically request ads from Google to show on their search pages and for some reason instead of implementing it themselves they used a company I worked for to do it so for some time a lot of the ads on ask.com were actually google or yahoo ads running through a random ad server I wrote. I remember having to move our systems to make sure we were in a data centre as close as possible to them and Google/Yahoo since we had (I think?)50ms to receive a request from them, contact google and yahoo for ad inventory, merge them and return it to ask to show on the page.

(This was all like 15 years ago now)