Apparently G+ is the second largest community. Wish TW had a voting package installed so we could see how many readers accept this as true.
Personally I believe that G+ does have a huge non active user base. However the active user base is just not there. My SEO friends and some other professionals I know through my job are on G+. However 0 real freinds are on G+ they are all chatting away happily on FB.