Gmail was down for a while today, and when it came back up I noticed the red text at the top Invite a friend to join Gmail!. Clicking on it brings up a new window which says that I have three invitations left. I plan to give one to a brother, and I haven't decided what to do with the other two yet. I will not give invitations to strangers upon request, so please don't e-mail me asking for one.

I think Google is giving out this many invitations in this manner in order to create a slightly more tight-nit network of Gmail users than just giving out invitations randomly. This way, Gmail users are more likely to get their friends and family into the service, and so there develops more of a community feel to Gmail. I don't think it makes that much of a difference, but I think it's a better approach nonetheless.