It's true they are not mutually exclusive. Closure is several related tools that can be used independently: a JS compiler (minifier + type-checker), templates, and very large JS library.
I don't know exactly which groups, but I have been told by an ex-Googler that they are used quite extensively by Google, sometimes in the form of Angular Dart. I have seen some proclaimed stats that they are used by over 120 projects by Google (I believe it was a slide from ng-conf).
I have also seen Angular on some Google pages in the wild, including the older Google Nexus pages.
If you click the options arrow on the chat feed (next to your name/status), there is a "Privacy Settings" option that allows you to specify which circles can chat with you.
fwiw, you can also specify which circles are in "Your circles" (the ones you broadcast to) and which circles you are just following in the G+ settings (https://www.google.com/settings/plus).
i don't know if i'll have time to finish anything, but if you would like to send it to me (email in profile), i'd be interested in looking it over and trying it out.
I think it would be more interesting if the number of requests were normalized based on either number of google users or the population of that country.