It’s a good idea – you can easily share your WiFi keys with people in your contacts list. However, Microsoft keeps the keys encrypted (how?) on their own servers to do this. This is not a good idea, turning the MS cloud into a treasure trove of WiFi passwords and locations. Also, if you’re giving out your WiFi password but the other party doesn’t have internet, the system doesn’t work – kind of making it a bit useless.

Tell a pal your password … and their FB mates will get it too

Source: UH OH: Windows 10 will share your Wi-Fi key with your friends’ friends • The Register