Didn't Google used to have a project that allowed readers to annotate the web? If I understand it correctly, it sounds like the author wants something similar

Didn't Google used to have a project that allowed readers to annotate the web? If I understand it correctly, it sounds like the author wants something similar only categorised by field of expertise instead of being a free for all (and not owned by one company). This would require some kind of moderation, in one form or anther. EDIT: Wikipedia says I was most likely thing of Sidewiki, which wasn't actually a wiki: https://en.wikipedia.org/wiki/Google_Sidewiki https://en.wikipedia.org/wiki/Google_Sidewiki