Evite does the same thing. My friends and I frequently forward our invitations around to each other with the note "If you're interested bump up my RSVP count o

Evite does the same thing. My friends and I frequently forward our invitations around to each other with the note "If you're interested bump up my RSVP count or add yourself with the 'invite more people' link on the right. I think it's fine in this case for the added convenience of not having to register/login. It's an invitation system not banking.