The Next Web reported on privacy issues with Windows 10.
Data syncing by default
Sign into Windows with your Microsoft account and the operating system immediately syncs settings and data to the company’s servers. That includes your browser history, favorites and the websites you currently have open as well as saved app, website and mobile hotspot passwords and Wi-Fi network names and passwords.
Cortana is a sexy spy in the machine
To enable Cortana to provide personalized experiences and relevant suggestions, Microsoft collects and uses various types of data, such as your device location, data from your calendar, the apps you use, data from your emails and text messages, who you call, your contacts and how often you interact with them on your device.
Cortana also learns about you by collecting data about how you use your device and other Microsoft services, such as your music, alarm settings, whether the lock screen is on, what you view and purchase, your browse and Bing search history, and more.”
Advertisers will know exactly who you are
Windows 10 generates a unique advertising ID for each user on each device. That can be used by developers and ad networks to profile you.
Your encryption key is backed up to OneDrive
Not necessarily a bad thing but something you should be aware of. When device encryption is turned on, Windows 10 automatically encrypts the drive its installed on and generates a BitLocker recovery key. That’s backed up to your OneDrive account.
Microsoft can disclose your data when it feels like it
We will access, disclose and preserve personal data, including your content (such as the content of your emails, other private communications or files in private folders), when we have a good faith belief that doing so is necessary to protect our customers or enforce the terms governing the use of the services.
Something to consider if you’re considering switching to Windows 10. Something to be aware of if you’re already on Windows 10.