http://spywareitdaiuyfo2sqb5vsg7mek5cjabdr73luhnda57t2hyuzg7yyd.onion/articles/steam.html
Steam also uses its social network features such as the user profile and friends list to broadcast a users program usage habits publicly. This spyware feature can be partially disabled by setting your profile to private, but it cannot be opted-out of if you are using the "friends" social networking feature.