Google Plus - aprox 40 million users as of 9/25/11
  
  I am just following up on research from Paul Allen 
  https://plus.google.com/117388252776312694644/posts/bGJPTALDkDe
  http://news.ycombinator.com/item?id=2747710
  
  I added a couple more recent samples (threw out a few names)
  
        07/04/11        07/09/11        09/21/11        09/25/11
         1,700,000       4,700,000       29,372,543      41,308,415 
                                
  Maring        3       9        50      65 
  Tomczyk       5       20       165     219 
  Lagana        7       13       100     150 
  Shireman      2       12       43      59 
  Tat   12      51              
  Tozzi         15      31       175     247 
  Trudel        9       25       212     286 
  Yasin         25      52              
  Greb  3       11              
  Toepfer       3       13       68      79 
  Cullinane     7       18       80      100 
  Fredenburg            3        23      35 
  Louderback            4        38      53 
  Santillanes           3        29      45 
  Murrey                4               
  Wilcoxen              8        20      40 
  Revelle               5               
  Parten                3               
  Lewter                6       23      30
  McTigue               9       49      61