10 Facebook and Twitter Mistakes That Could Cost You Your Job
Kevin Colvin will forever live in Facebook ignominy as an intern who claimed a family emergency on Halloween...but his co-workers saw a time-stamped picture of him dressed as a fairy and holding a beer. His boss fired him, CC’ing the entire company and including the picture. Now, getting caught online while playing hooky is called "pulling a Facebook Fairy."
A better career move: First, don't friend your co-workers on Facebook (that’s what LinkedIn is for). Also, don't check in on Foursquare when you’re supposedly in bed.
But Danielson points out that staying offline isn't enough: “Somebody could check in on Foursquare at the same place and say you were there, or post pictures of you on Facebook." Stuff happens, so the easiest way to be safe is to just keep things above board.