Survival Arts

I'd love to know how & why Gmail does its thing

I mentioned yesterday that Google's Gmail service had given me 6 invitations (they'd originally given me 2) yesterday, and that I was giving them away. I got 3 takers within minutes, leaving 3.

This morning, I notice that I had not 3, but 6, invitations left. I immediately gave away two more.

The thing is, several other people I know have Gmail accounts, but I've been told by some of them that they've only ever been given a grand total of 2 invitations, with no replenishment. I'm not sure why I keep getting more... I wonder what rules Google's automation uses to determine whom to replenish with invitations? I'm guessing that it may be a side effect of the fact that I receive mail from a very busy mailing list to that account. Invitations may be granted in proportion to use. Anyone have insight to share?

By the way - to pre-empt the inevitable request from someone I've never heard from previously - I should add the caveat that I'm only giving these invitations to realspace friends or those of my online acquaintances with whom I'm friendly.