Are energy drinks bad for you?

We have all been there.  It was a long night and you tossed and turned.  You may have had a late night of work followed by a dinner that haunted you.  You may have even had a nightcap or two.  Now, it is 9 am and you are dragging at work or school.  Now, that energy drink is calling your name.  It really is easy to give in and reach for a tall, monster-sized drink of instant octane in the cooler.  The questions are if they are really that bad for you or is this just hype from the healthy nuts?