I recently had the privilege of welcoming the Gmail Rep to the Search Engine Watch Forums. In my Welcome GmailRep thread, I decided to ask the question; how do Gmail invites work? Specifically, how does Google decide the 'who, when and how many' in sending gmail invites to gmail account users and non gmail account users.
As expected, the answer had to be somewhat vague (don't get me wrong, I do not blame Mr. GmailRep). The answer from the official Gmail representative was (and I quote) "invitations are provided to Gmail users on a random basis. Some users may receive more invitations than others and the invitation process sort of ebbs and flows."
If anyone has more information or has seen any pattern to this "random basis", I would be interested. I have a feeling the invite algorithm is fairly simple at the present time, but for some reason, I want to know. :)