Google's ad-insert can see the referrer field; they can confirm that the site is really linked from the originating site. With their toolbar and analytics data and giant AdSense network, they know better than anyone how much traffic an outlink from these sites sends.

So while they know the surge is different, they should also know exactly how it's different, and that it's not "bot activity". Holding back ads from all such ephemeral traffic would make sense -- and serving appropriate lower-value ads the most sense -- but banning the account does not.