Earlier quoted context omitted.
Seconded. Compete's numbers are just made up. I know for sure they are off by more than an order of magnitude for reddit (or at least were a year ago).
Most of the traffic tracking on the web involves plugins (generally in the form of a toolbar). I don't know about you guys, but I haven't had a 3rd party toolbar in my browser interface in a long time. Compete, Alexa, etc. they're all tracking people who don't understand technology.
That would mean that G+ is even stronger as it seems mainly popular with the tech crowd.