“When you share Wi-Fi network access with Facebook friends, Outlook.com contacts, or Skype contacts, they’ll be connected to the password-protected Wi-Fi networks that you choose to share and get Internet access when they’re in range of the networks (if they use Wi-Fi Sense). Likewise, you’ll be connected to Wi-Fi networks that they share for Internet access too. Remember, you don’t get to see Wi-Fi network passwords, and you both get Internet access only. They won’t have access to other computers, devices, or files stored on your home network, and you won’t have access to these things on their network.”
WiFi Sense will automatically connect you to detected crowdsourced WiFi networks, acquire network information and provide “additional info” to networks that require it (it’s not clear exactly what constitutes additional info), and can be used to automatically share your WiFi password with your contacts on Facebook, Skype, and Outlook.
On a practical level, the risks from WiFi Sense are small. But from a best-practices security standpoint, it’s far from a great idea.
Oh, my God, disable NOW:
Settings->Manage WiFi Settings->Wi-Fi Sense
Turn it off