Google has quietly posted a notice that they are "sunsetting AdSense" for Google Sites. It appears that after August 30, 2013, the AdSense ads on Google Sites will no longer be able to be edited or added to. You can delete them.
It is however unclear if you leave the ads on the site, will they still earn money for you after August 30th.
Here is the notice:
Some important changes are coming to AdSense on Google Sites. By August 30, 2013, it will no longer be possible to make updates to AdSense on any of your Google Sites.No change is required on the part of AdSense users. Any ads that you currently have running will not be altered or removed, though you’ll be free to delete ads yourself. However, it will no longer be possible to edit or add new AdSense ads to your existing site or to new pages.
I'll try to get more information from Google on this change. Although, I think the reason is that I assume the majority of the sites on Google Sites are spammy.
Forum discussion at WebmasterWorld.
Update: Google has updated the message to clarify that ads already on Google Sites will continue to earn money. Here is the revised text:
Changes to AdSense on Google SitesStarting August 30th 2013, it will no longer be possible to modify AdSense ad code on Google Sites pages. However, any ads you’ve previously placed on Google Sites will continue to show, and you’ll be credited for all valid earnings.
No change is required on the part of AdSense users. Any ads that you currently have running will not be altered or removed, though you’ll be free to delete ads yourself. However, it will no longer be possible to edit or add new AdSense ads to your existing Google Sites site or to new pages.
Please be assured that this update will not affect the standing of your AdSense account or ability to show ads on any other websites you own. If you’d like to show ads on other websites, simply log in to your AdSense account at www.google.com/adsense to generate new ad code at any time.
