Posted October 21, 2012
Did you take any screenshots of the event? If so, you could probably report the person on SteamRep: http://steamrep.com/
nmillar: Do not trade with TurtleDove (Steam ID: http://steamcommunity.com/id/TottalyAwesomeLOL/) - just lost a copy of Nuclear Dawn to him - gave me a duplicate code.
That would at least make it a bit harder for the person to do it again.