I wonder if there could be be something like a required "check-in" about two weeks before the swap starts. If a member doesn't "check-in" within a week, then the host gets a notice. If contact can't be made via tree-mail, email, etc, then the host could remove the member from the swap. It seems like some people sign up months ahead of time, add seeds and then forget about it or have bad things (like house fires) happen.
