I was under the impression that while it is only plays by members that are counted, Terry has a program in place to give credit for estimated plays by guests.
It seems to me that for every member who plays a game, the count goes up by three, because it averages out that way (two guests play a quiz for every member who plays it).
"To insult someone we call him 'bestial'. For deliberate cruelty and nature, 'human' might be the greater insult." - Isaac Asimov