Indeed. But on the other hand I don't think Google would disallow or block ads for Facebook. Their strategies differ. Google thrives with an open web, Facebook is a walled garden. But yeah, no scandal here.
[1] AdWords - Wikipedia - http://en.wikipedia.org/wiki/AdWords
Facebook is taking the stance what Microsoft took a few years ago - getting in the way of it's users and making choices on behalf of them.
On the other hand by being open, Google has made a ton of money from it's competitors like Groupon which spends a big chunk advertising on Google.
I don't know if Facebook has made an official comment on this but from here on I think things might get interesting.
It seems to me that twitter are the ones supporting the open web now.