I would bet that you use Facebook; most people are on the social network today. If you do use Facebook you need to be aware of a new feature that the site has added for developers that will share more of your private information with marketers and apps if you allow it. The new feature will give access to your mobile phone number and physical address.
On the surface, the new feature seems useful and would allow things like ordering of products online without having to enter your shipping details. The fear for some users is that rouge apps would access the information and then sell it to marketers. That would allow more spam to your real world mailbox and more calls from sales douches to your mobile.
Facebook's Jeff Bowen said, "We are now making a user's address and mobile phone number accessible as part of the User Graph object. Because this is sensitive information, we have created the new user_address and user_mobile_phone permissions. These permissions must be explicitly granted to your application by the user via our standard permissions dialogs."