Online start-up businesses run by young adults are an increasingly common phenomenon. A commonly overlooked demographic, however, are the real youth — those under 18 years of age. With online businesspeople facing very low barriers to market entry, many tech-savvy kids are getting in on the act and taking advantage of the opportunities that abound. While these entrepreneurs are more the exception than the rule, some of their successes are highly notable — myyearbook.com was initially founded by two high-school students, yet at one stage was the third-most popular social networking site in the United States, behind MySpace and Facebook. Of course, Facebook’s Mark Zuckerberg was still in college when he established one of the most popular social networking sites in the world. (more…)