Moochers rejoice: Valve is bringing game lending back in a big way. The company announced today that a new Family Sharing feature is coming to Steam in the near future, and a thousand Steam users will begin beta testing the Family Sharing system in mid-September. Early adopters can volunteer for testing duties by joining Steam's new Family Sharing Group.
Once you have access to Family Sharing, there are two ways to share: you can toggle an option in Steam's Account Settings menu to make your library of games available to anyone who logs into Steam on your PC, or allow others to access and download your previously installed games remotely--Valve will be updating Steam to allow users to request Family Share access.
It's important to note that this remote request system is tied to hardware: if you request access to a friend's Steam library and she approves, your PC will be authorized to download and play games from her library.
Your Steam cloud saves and achievements will remain separate, but borrowers can play the expansion packs and downloadable content in your library. Borrowers cannot purchase DLC for games they don't own, and region restrictions apply when borrowing games. Sorry, Australian Saints Row IV fans.
Valve is also taking pains to assure users that in-game items will by and large be unshareable and tied to accounts, not the base game. You'll be able to borrow a friend's copy of Team Fortress 2, for example, but you won't be able to try on all the sweet hats they've earned. This suggests that games which require subscriptions to play--The Secret World, Final Fantasy XIV and the like--won't be worth borrowing, since you must pay for an account on a third-party service to play the game.
You may authorize ten devices to share your Steam library, but only one person can be playing games from that library at any given time. The lender holds the power here--you can always access and play games in your Steam library. If someone else is borrowing a game from your library when you want to play they'll be shown a warning and afforded a few minutes to either purchase the game themselves or close the game.
Steam's new lending system sound suspiciously like the Xbox One 10-person family sharing system Microsoft proposed and then quickly cancelled earlier this year. Many users mourned the loss of that sharing system, and now that Steam is taking the lead on digital lending it seems likely that Microsoft will make good on their talk of reviving game sharing down the road.