I wonder how many of the visits were due to GOOG merging their properties and forcing people into a visit... I think I gave them a click and a few seconds when I was checking out how the consolidation of power was being force fed to users.
But, lets give Google the benefit of the doubt that people actually wanted to visit, and then crunch the numbers...
But that still puts Facebook at a grand total of approximately 7 billion visits for March, or just over 114 times the traffic of Google+.
January Comscore report put average time on site for Google+ members at a mere 3.3 minutes for the entire month. In contrast, Facebook members spent an average of 7.5 hours on the site in January.
That means the Facebook to Google+ "engagement factor" is somewhere in the range of 15,000:1