Its no surprise that your employer or future employer is watching you. First your company buys software to either directly do this or out sources it. There are many places that sell information that will list all your SSN, previous addresses and relatives. Once that is acquired, The software is used to data mine information from social media, LinkedIn, Google your name, etc. and then they build a profile. This way your company can tell if your looking for a new job or doing something that they do not agree with. Just because its not against the law, does not mean your company won't terminate your employment because of it. This is definitely being done to any one with a security clearance. --- Just remember, you are what you Tweet.
My employer blocks websites that supposedly interfere with productivity, and a message with the banned category appears when access is attempted. There are the usual categories of "Shopping", "Sports", "Religion", and so on, but my favorite so far is "Health". Apparently, good diet and exercise habits are the last thing you want your employees concerned about.