Sorry for asking a question of potentially very short validity. (Though it's been this way for at least one week.)
I've noticed that the ad that sometimes appears in the side column on the right on at least Stack Overflow and Server Fault links to a URL that starts with
http://googleads.g.doubleclick.net/pcs/click?. However, the ad that appears here always appears to be an internal ad for Stack Overflow Jobs. Here's a screenshot (look at the URL in the status bar).
Would it cost Stack Exchange money if I clicked this ad? (And aren't they paying just for showing it?) (Or does Google Ads show internal ads for free, and is there some benefit (e.g., analytics) in using Google Ads even for internal links? (Or is there some other explanation for all this?))
Update: Unless I'm missing something, this is not a duplicate. The suggested page (All sites will be switching Ad Servers on October 1) does not appear to address why they serve ads for their own product on their own site over Google's ad network, which seems to me like it would incur fees.