Teachers, coaches, colleges/universitites, employers are watching what you put out there and, right or wrong, there are some pretty life changing consequences for those "off the cuff" tweets, posts, pics and videos. Unfortunately, it isn't just about what you post either, a "tagged" photo of you in the background can be just as incriminating.
Privacy is a thing of the past, and unfortunately, there will always be a smartphone ready to document our "brain fart moments in life" for eternity. Think twice before you post and before you "friend" 3000 of your nearest and dearest acquaintances.