yah, this is a good idea (imho). i've done this for a 7.2.2 site where the user base (already regged) get a certain number of 'invite codes' issued to them, based upon varying criteria -- lenth of service, stature.. bla ble --
then can then do an invite ala Google invites and sign up..
works fine and gets the community active to try and bring more peeps in as well as doing a semi pre-screen of the types of members who will be signing up..
good stuff
