from now on Google ads are visible only on published articles. Drafts cannot be crawled by Google, resulting in an error 404 when trying. For once, Google doesn't like that, and secondly the initial ads after publishing a new article should have a better matching content. We'll see :)
Anyhow, this has been a very quick update and we haven't yet decided which way to go: Showing a dummy image instead of the ads or not showing anything - as it is right now.
Many thanks to Sybille for this great hint on the matter!