Embarrassing Spam in Groups

I use Google Groups to follow discussions on the AdWords API, as do many other users of the API. For the last few days, every day, there have been 25 or so porn spam posts appearing. If it were a less serious group, maybe I'd have less reason to complain, but this is a discussion group hosted by a Google product, discussing a Google product, linked to from the official AdWords API blog, and all we are getting is spam. Surely Google can fix this?

In parallel, Gmail is doing a sterling job catching spam, and there are very few genuine emails ending up in the spam folder. Except that is, for various official Google emails. Go figure!