Facebook is expected to announce that it has reached the 500 million user mark this week. That's half a billion people in just six years.

It seems like only yesterday Facebook was a students-only site birthed from a Harvard University dorm room. Now it's the most visited site on the net and a multi-billion dollar empire.

Putting the half-billion-member-mark in perspective, The Washington Post reports that "the population inhabiting Facebook now equals that of the United States, Japan and Germany combined. Or, two Mexicos and a Brazil."

In an interview with All Things Digital, Randi Zuckerberg, Facebook's marketing director, said that the site plans to celebrate its milestone with "Facebook Stories," a collection of real-life blurbs from Facebook users about how the social networking site has impacted their lives.

Users are encouraged to visit the http://www.facebook.com/help/contact.php?show_form=user_stories to submit their yarn in 420 characters or less. The stories will then be organized by geographical location and by themes such as "finding love," "coping with grief" and "natural disasters." If you choose to tell Facebook something about yourself, keep in mind that Facebook reserves the right to publish it any way it chooses so no privacy complaints.

Plenty of them are fake or duplicate accounts owned by one person.. this is still crazy though.