Now that LinkedIn is a decade old and has 225 million members, its fastest-growing demographic –30 million and counting—is students and those who are three years or less out of college. Though LinkedIn’s user agreement says that members agree they are at least 18 years old, I am going to make a recommendation and a prediction: High school students should start LinkedIn profiles now. I predict that LinkedIn will soon drop its age threshold or eliminate it altogether. Consider that Facebook’s threshold is 13, and the site has hundreds of thousands, if not millions of kids under 13 using it every day. Unlike Facebook, LinkedIn has no place to enter a birth date.