It's worth nothing that the FCC has a speed test app which is trying to gather exactly that kind of data:

http://www.fcc.gov/document/fcc-unveils-mobile-broadband-spe...

(source available here: https://github.com/FCC/mobile-mba-androidapp ).

It's currently more focused on mobile networks, but it also gathers Wi-Fi performance data as well. And given recent developments, I wouldn't be surprised to see the FCC broaden that focus.