When it comes to social networking, college students tend to put their best face forward. Online directory Facebook connects people through social networks at schools. Students post photos and information about themselves through online profiles published on Facebook.com. A Facebook requirement is that users have college e-mail addresses; some faculty, staff, and alumni also join. The site was launched in 2005 by five undergraduates at Harvard University, led by Mark Zuckerberg, as an online version of the Harvard Facebook. (The name comes from books of freshmen's faces, majors, and hometowns that colleges distribute to incoming students.) Investors include Paypal co-founder