Some collect information you expressly give them, like your credit card and telephone numbers. Others gather data based on how and where you use their services. This might include anything from device and browser information to location intel. And some of it gets really specific — think about your last search query or ad click. It’s probably all “fair” game.

Depending on the type gathered, social networks use data to enhance location services and target advertising (now you know why that sunglasses website you visited three months ago follows you all over the web). A few social sites even share certain information with marketers and/or third-party partners