Jean-Baptiste Quéru (JBQ) was the maintainer at Google of the Android Open-Source Project, but binary blobs for GPU drivers got the best of him. Jean-Baptiste wrote on Google+, "Well, I see that people have figured out why I'm quitting AOSP. There's no point being the maintainer of an Operating System that can't boot to the home screen on its flagship device for lack of GPU support, especially when I'm getting the blame for something that I don't have authority to fix myself and that I had anticipated and escalated more than 6 months ahead."
The flagship Google Nexus 7 doesn't have AOSP support since the device relies upon a Qualcomm ARM SoC and there are no vendor-backed open-source graphics driver. There is the Freedreno project for some open-source Qualcomm graphics support, but it's reverse-engineered and done without Qualcomm's support and isn't yet in a state for officially supporting hardware, especially on newer hardware.