I'm not sure where GWI gets their information, but the number 343m seems a good match to G+'s "total actives", as the last result we shared publicly was 235m bu

I'm not sure where GWI gets their information, but the number 343m seems a good match to G+'s "total actives", as the last result we shared publicly was 235m but that was almost 2 months ago. The number of G+ accounts was already much bigger due to migration, but the number of "stream actives" (people who actually used plus.google.com, or the mobile clients, in the last 30 days) was lower at 135m (again, on Dec 6). Current numbers are bigger, the stream actives may or may not already be in the ballpark of GWI's claim, but AFAIK we didn't yet share new numbers after Dec 6. Rest assured though that when we officially share "stream active" numbers, it's real stuff no tricks. GWI's comparison is difficult because not all social networks disclose the number of strictly active users -- how many people recently checked their stream/profile/whatever. Most notably, Facebook only publishes the biggest stat of total number of open accounts.