Wi-Fi Sense is a feature built into Windows 10. You may see a pop-up saying Wi-Fi Sense needs permission to use your Facebook account. It also works with Outlook.com and Skype contacts.
This feature allows you to share Wi-Fi login information network names and passphrases with your friends. Its designed to automatically connect Windows 10 devices to shared networks.
What is Wi-Fi Sense and Why Does It Want Your Facebook Account?
At least you can opt-out easily. There's no way I'll use that feature. If at least I was able to pick the people I wanted to share my information with, then okay (since I would share it with family members when I go over or they come over), but now, I won't use it. I'll probably find a way to disable it altogether too.