> Note to other submitters, the following is a good edge case to test:
> 
> Luke1 Skywalker <luke / theforce.net>
> Luke2 Skywalker <luke / theforce.net>
> Luke3 Skywalker <luke / theforce.net>
> Luke4 Skywalker <luke / theforce.net>
> Leia Skywalker <leia / therebellion.org>
> Toula Portokalos <toula / manhunter.org>
> Gus Portokalos <gus / weareallfruit.net>
> Bruce Wayne <bruce / imbatman.com>
> Virgil Brigman <virgil / rigworkersunion.org>

I thought it might be a good idea for me to explain exactly what is 
interesting about this test case.  There are 5 Skywalkers and 4 
non-Skywalkers.  So the moment a non-Skywalker is assigned to another 
non-Skywalker, a solution is impossible.

(Gavin, your solution warned me that the input contained duplicate 
e-mails... nice!)