Since your followers on Instagram are more than likely just friends from Facebook, they already know by the 47 status updates that you have "stepped off the plane," "just watched some lady grab the wrong bag at baggage claim," "tried to hail a cab - French cabbies suck," "OMG loving my hotel suite," "beach life - I could get used to this!" and whatever other pointless updates you left. There is no reason to take a picture of yourself on vacation, or better yet, have someone take a picture with your phone while you act like you didn't know it was being taken, then post it to Instagram using the hashtag "#vacation." The reason you are on vacation is to relax and get away from everyday life. That includes Instagram.
The point of Instagram is to share your life with others in the form of pictures. One day, though, someone thought it would be funny to take the picture of your drunk/unconscious best friend with text laid over it that said "Keystone Light? Turn off the light!" (Notice how that wasn't funny?) You're sorority girlfriend who posts esteem-building things like "Don't ever let anyone tell you aren't good enough -- you are perfect just the way you are" is just trying to let people know that she isn't a selfish jerk. She is a selfish jerk, and that is called "being fake."