Do you like sharing games with your friends on Steam? Well good, because you can still do that - you'll just need to assure Steam that you actually know your friends before they can start digging into your library. An update to the Steam Family Sharing community page explains that in addition to authorizing the machine your friend accesses your library from, you'll also need to give clearance to the account they're using.
You'll now be able to grant 10 accounts and 10 machines access to your games and DLC, unless of course they require a third-party key or registration. The post explains that the added need to clear accounts allows a library's owner more control over who is accessing it. The change also decreases "the risk of VAC or other bans resulting from an unknown user accessing and abusing shared games on an authorized machine."