Facebook's User Growth Continues to Decrease while Google+ Adds 625K Users Daily

Facebook's growth rate for its user base is continuing to decrease while Google+'s user base is growing, and at the same time when Google+ just experienced its biggest traffic month of all time.
As All Facebook reports, in the 1,001 days from April 1, 2009 through Dec. 28, 2011, Facebook added 609M, with averages of around 600K per day and seven per second. But according to Optim.al, that growth rate has tapered off.
While Facebook's growth soared to 8.39 users per second from July 2010 through March 2011, it slowed to 7.02 users per second from March 2011 through Sept. 2011. From Sept. 2011 through Dec. 2011, growth dropped to five users per second.
Last month, an unofficial Googler revealed how Google+'s growth is accelerating, noting how it recently passed 62M users and adds 625K users per day. Still, Facebook has...