For anyone who grew up in the era of cartridges, floppies, and discs -- physical media -- you'll know the nostalgic feeling of being able to loan games to friends. Pass off an Atari or NES game and let someone else play it, maybe even borrow one of theirs in return. Those times died with the advent of online distribution and the obsessive approach to combating piracy. Steam is a blessing and a curse: It's got great sales, improves accessibility to games, and is a convenient form of DRM that most people can agree with; at the same time, we're putting all our eggs in one basket, support is questionable, and the DRM is still, well, DRM.
Valve has been testing Steam Family Sharing with a crowd of beta users for a while now, but they've finally just launched the full update. Family Sharing allows users to grant game library access to "family" and family, ultimately letting us share games with one another.
Steam Family Sharing works between a maximum of five accounts with one game library between them, usable over ten systems. Offline game sharing is no longer possible, so users sharing access must remain online to play the games. Accounts separately store their own save data, achievements, and other individualized information for the account; this means you won't be bumping into each other in your save files, theoretically.
The owner of the game library (primary account holder) dictates who gains access to the games library and can kick players off if they'd like to play. The system operates on standard check-in/check-out mechanics -- only one user can be assigned to each game at any given time.
Read more here: http://store.steampowered.com/sharing/
- Steve "Lelldorianx" Burke.