As a theoretical example, Microsoft may compare the personal information between both Netflix and Microsoft's account to ensure both match.
"Protecting your account from unauthorised access and fraud is a top priority for us. It helps keep Xbox Live safer and more secure for everyone," reads the statement from Microsoft.
"That's why the TOU now asks all users to commit to keeping their contact information up to date. By the way, now is a great time to make sure your security proofs are valid and accessible to you.
"More app experiences available via Xbox Live are provided by a partner with whom you may have a separate online account. If you choose to link this account with your Xbox Live account, we confirm key data points across the accounts by sharing data such as your name, address, email address and date of birth with the partner. In this TOU update, customers agree to allow Microsoft to share this information in this manner."
In July it was revealed that Microsoft allowed the NSA to access emails, video calls and SkyDrive data on users' Microsoft accounts.
In October a senior Microsoft executive downplayed speculation that Kinect could be used as an advertising platform, where a user's emotional state and response could be captured and sent to the advertiser, or as a device that captures video information without permission.