Ok, I will explain how it works because you don't want to do any of your own background research into anything:
In countries such as India, Russia, China, these countries less strict on copyright laws, piracy is rife. As such, to sell a game at the retail price that you or I pay would not be worth it for the developers as they are selling very few units due to everyone else just pirating the game. That and the people there would not be able to afford the game anyway because the average income is so much lower. It is always either one of these factors or both.
What do they do to ensure more sales there then? They drop the price... A lot. So much so that sites such as CJS are able to buy the games in bulk from such countries, ship them over here and then re-sell them at a price that is higher than what they bought them for, yet substantially lower than what it is sold for here, so they make a profit and we, the customers, get a better price.
CJS receive the keys, scan the image and then dispose of the box. They will alternatively sell the discs for some as just the disc to people without access to the installation media, but this is without the key.
They do not re-sell keys, they do not re-use keys, nobody has access to the key once it is scanned and sent on to you, and as a key can only be activated once through Steam/Origin, it does not matter if somebody else got it, they can't do anything with it; your account can't be found from it, you can't get banned for it, you can't be locked out of the game because someone else is playing it, because they can't play it while you are.
An example of what you get, from my own purchase made, obviously with the key blanked out:
http://postimg.org/image/rphwaxhz5/
I know it is unused as I have checked pbbans, the only names linked to it are those used by the clan member that I bought it for. I know it has no bans associated with it, again because I did a background check on the GUID, in fact it is so clean that it has been used in CoD4 Leagues, which is the reason that it was purchased in the first place.
Note that the CoD4 key is not a Steam/Origin activation, it is a standalone key as CoD4 is not activated through Steam or Origin. Even near enough a year after the purchase (02/12/2012), the key is still clean and untouched by anyone else.
Do you have any more theories about it?