It would appear that Google has introduced a new feature in its Adsense process. If you check the image below, you will see outlined in red a small Previous and Next pair of buttons at the bottom left on the Adsense ads that were shown this evening.
For avid Google Ad fans by clicking on either of these buttons you can have a veritable horizontal slide show of other Adsense ads. That gives Google and Adsense advertisers many more kicks at the can. It does not appear too often but presumably is used when there are many more advertisers than can appear in one ad block. It would seem to be a win/win/win proposition for all.