The fact that high-schoolers couldn't join Facebook for years didn't seem to hurt it too much.
Edit: downvoted?
To quote Wikipedia:
The Web site's membership was initially limited by the founders to Harvard students, but was expanded to other colleges in the Boston area, the Ivy League, and Stanford University. It gradually added support for students at various other universities before opening to high school students, and, finally, to anyone aged 13 and over. However, based on ConsumersReports.org on May 2011, there are 7.5 million children under 13 with accounts, violating the site's terms.
