Typically, most information that is gleaned from your internet searches, social media networks, blogs, etc. are used to better match products and services that fit your profile. Advertisers see this as a great tool for giving you the information that would most benefit you.
There are more sinister uses for your personal information. People that are in the business of stealing identities can find a wealth of information about you, including addresses, birthdates, names of relatives, and job history. How much of that information can be used to fill out a fraudulent credit card application?
Another cause for concern is how your personal information is being stored. Perhaps, innocently enough, your preferences for products and services, along with much of your personal information is being used for advertising. But who else can get to that information.
Big Brother is a term used for governments or other entities that control information. If Google technically owns all of your emails, with all of the personal information contained within them, as well as your calendar entries, pictures, etc., could they one day be considered a Big Brother type entity? Have you ever watched the Terminator or Matrix movies?
Ok, you have scared me straight. Now what?!?!?!
Facebook has recently come under fire for how they use your information. They do have built in protocols that you can adjust to minimize the information you share. Google, and most other sites that store your information have these same controls. Sometimes, navigating the security settings can be a little tricky. Simply type in a phrase like Facebook Security Settings or Google Privacy Settings into a search engine, and you should find many articles on how to manage your privacy settings.
Unfortunately, personal information about you may come from other sources. Social media lets people share information about themselves, and their friends, family and other associates. You may not be able to always control the information that is floating out in cyberspace.
A good rule of thumb is to not disclose any information online that you would not disclose in public.