Too bad they don't sell CD Keys seperate for people who already have the game so you can have two accounts with one game. But to make this more difficult for people to merely install the software from a friend then buy a key, they would have to do it from their setup account screen that would lead them to a secure site on the net where they could buy another account via paypal for ten or fifteen dollars for four extra spots.
I just think if they somehow linked it to your existing account to where only you could access this page or what not through the client, a type of java window or something that wouldn't work if you copied the address or something, it'd be cheaper than buying another copy but allow ANet and NCSoft to get a little extra money that would be optional, not a requirement
I know this sounds confusing but I'm certain it could be done somehow... Just a suggestion to make everyone happy in one way or another...