This module fits my use case perfectly, but unfortunately suffers from a serious flaw (unless I'm missing something) of not being able to limit sent invites per user and/or node.

Without some sort of limitation users can use the system to spam content.

Both "Invite" and "Forward" modules have some sort of flood control. I've tried to make an adjustment where I thought needed to hardcode an amount in, but it didn't seem to work. Perhaps someone can take what I have and figure out a solution.

  // Has anyone been added to the invite?
  if (!count($emails) && !count($users)) {
    form_set_error('emails', t("No one has been added to the invite."));
  }
  elseif (!count($emails) > 10) {
  form_set_error('emails', t("You may not enter more than 10 recipients."));
  }

}