But I'm assuming second hand sales are off, or am I mistaken? I've got a hard copy of the game. When I first fired it up, it automatically connected with Steam and asked me to type in the serial number of my copy and my email address, plus I needed to respond to an automatically sent email to verify that this email I gave was indeed mine.
What I'm thinking is that if I want to sell my copy on, or bring it to charity, this will not work. Somebody else can't do anything with it, as upon install it will ask for a serial number and associated email.
That's why I was saying earlier that things like the carboot sale or Ebay were off for Civ 5. I was talking about second hand sales specifically, not retailer deals. For Anandus: 'Carboot sale' would be called 'vlooienmarkt' in Amsterdam. Ebay is also used for new stuff, maybe that blurred my point.
If now sales between people on Steam or going on, as I read here, then I understand that, because with cooperation of Steam you could still do it. If they see the sale and agree with a new email address being created for that copy of the game, you're good to go.