4 more invitations

Gmail is giving me 4 more invitations to use:

Invite a friend to Gmail!
You have 5 invitations left

Thanks for using Gmail and helping us improve the service. We're ready to expand our test to a few more users, and because you've been a trusted early tester of Gmail, we're looking for your help. Please invite a few more people who you think would like Gmail and could help us make it even better.