"HTTPS-enabled sites require that all content on the page, including the ads, be SSL-compliant. As such, AdSense will remove all non-SSL compliant ads from competing in the auction on these pages. If you do decide to convert your HTTP site to HTTPS, please be aware that because we remove non-SSL compliant ads from the auction, thereby reducing auction pressure, ads on your HTTPS pages might earn less than those on your HTTP pages."
But only in the sense that the article text could say e.g. "implement the authentication algorithm according to illustration #42" and illustration #42 could have been maliciously replaced with an image showing an incorrect implementation, right?
A script served over an insecure connection, on the other hand, would give the attacker access to the DOM and compromise the entire page (and other pages on the site with AJAX).
So does the fact that ads need to be served securely imply that they have the ability to execute JavaScript in the context of the page? By serving ads (whether encrypted or not) am I trusting every advertiser on the network with the session cookies of all my users, essentially allowing them to intercept communications between the site and its users?
I do not believe that I can improve on their systems.
Or, you know, loading untrusted javascript onto your page could also jeopardize the security of your site.