According to an early 2013 report from ComScore, Facebook still maintains the lead for American user engagement for a single web site - averaging a minute short of 6.75 hours per user in the month of Mar 2013. While this number is a decline from the same period in 2012 (with an average of nearly 7.25 hours per user), it's obvious that American Facebook users spend a considerable amount of time on the site - more than any other social media site - revealing facts both mundane and interesting about their lives - facts that might be of interest to other people and companies, including those with ill intent.
In fact, according to a study by Alessandro Acquisti discussed in a TED Talk, American employers often judge job candidates who post to social media more harshly than equally skilled candidates who did not post - regardless of whether posts were negative or positive or not even relevant to the potential employer.
How potential employers find your Facebook information about you is beyond the scope of this post, but below handy infographic from bestcomputerscienceschools thoroughly covers some relevant security and privacy statistics and offer some tips to guard yourself on Facebook.