The following note now appears next to the Ad Style section of the Adsense interface for creating new ads and editing existing ads.
Ad style
(AdWords ads only)
So this must mean that third party ad style is now controlled by the advertiser or the advertising network or that Google is using a default style for third-party ads. This seems to take even more control out of the hands of webmasters where layout and styling of an ad is concerned. Interesting. Haven't even wrapped my head around the implications yet but it's got the wheels spinning and it will be interesting to see what effect this has for people who have third-party networks turned on. Could turn into a smorgasbord of styles (or not). We'll see I guess.
Added: Could this be a sign that third-party networks are lashing back at google for their recent and drastic ad style modifications?