Every year google post some interesting stuff on April 1 to fool. This even thay have posted in adsense blog its quite interesting :

We're happy to announce the launch of AdSense for conversations, a new type of monetization solution that "puts the 'context' in contextual advertising". Now, in just a few simple steps, you can begin displaying ads that are relevant to the topics you're discussing -- in an unobtrusive screen above your head.
read here