Recently the internet just blew up about Windows 10 storing your wifi passwords in the Microsoft cloud. This is what Google and I believe Apple have been doing for how many years now with mobile? I don't get why when it's happening with a computer they suddenly get butt-hurt about it [excuse my Canadian language].
That's not the issue. The problem is that they ask you if you want to share those details with your contacts. Let's say I bring my Windows 10 laptop or phone (that I've connected to my Outlook or Facebook account) round to your house and you give me your WiFi key. If I choose to share the connection with my contacts when I join suddenly my friends, family and the plumber I emailed last year can also join your WiFi, just because I have them as contacts. It's not granular either, is literally all my contacts. The only ways you can stop that happening are either putting the key in for me and choosing not to share, or modifying your WiFi name to put an _optout in it (and obviously rejoining everything you ever joined to it).
Microsoft claim that people connecting to shared WiFi can't get to the rest of the network, but they've not said how they're enforcing that so people are suspicious that it'll be hackable. The whole idea seems open to abuse and pretty risky for a small convenience.
That said, I've yet to see this option on Windows 10 Enterprise, so I don't know if it's only available in Home editions or if they backtracked on it.