FireDrakeZ: Never share your login name and password to a stranger. The other guy could easily change those information while he was logged in and lock you out.
erwin87: There is another option - on steam it's allowed to share library with 5 friends and it's legal so I can share since I have no fiends ( hah it's sounds little weird :D )
Hey, you got the point. Of course, it is not only about the security of your personal account, it is totally incorrect understand of Steam rule. Actually this was not a new issue as there were some posts are doing the same thing, but you actually misunderstood Steam rule. It just like same thing happened in GOG that some people believe DRM-Free software is available to share with anyone.
Let me quote some details from Steam rule: "Steam Family Library Sharing allows family members and their guests to play one another's games while earning their own Steam achievements and saving their own game progress to the Steam Cloud. It works by granting family members' access to your games on a shared computer."
In Steam rule, it seems like players can be allowed to share library with 5 friends but it doesn't mean that you can share with the strangers which I mean someone you just met on the internet or in real life, and absolutely not the people you are trying to make friend for using Steam Family Library.
It is kind for GOG to include DRM-Free and Steam to include Family Library Sharing, these are not easy for the market, not all the developers would allow, so we should be clear about the rule and enjoy these extra service.