I've seen those type ads a number of times when searching for articles on recent news events. They are promoting the news source as opposed to news.
It's probably not a bad tactic. As news breaks, there are few advertisers targeting the key words but possibly lots of people searching for the news. The television network, magazine or whatever gets the opportunity to draw in a visitor who might click on ads on their site or at least drive up page views.
I can't be sure because I'm not doing click tracking, but I suspect these CNN ads have been very good for me. I run two different news sites in different niches, both of these sites have had these CNN ads on topic fitting right in with the rest of the news on the site, and I imagine since my visitors are there to read news, these ads gets very high CTR on my sites.
I know the CTR and EPC of one of my sites went up the same day CNN was running an ad on that day's hot story in my niche.
I hope they keep running these! This is exactly what we expect from Adsense, an advertiser offering our visitors something they're interested in, and not trying to rip them off.