Well, I still need 2 copies of Civ 5 to play multiplayer with my son:

  > CAN A FRIEND AND I SHARE A LIBRARY AND BOTH PLAY AT THE SAME TIME?
  >
  > No, a shared library may only be accessed by one user at a time.

Now, I was (and still am) fine with that since it has provided so much entertainment, but for many games that would not be true...