Five years ago, hardly anybody had heard of Facebook. Today, it seems that there is nobody in Israel or the world over who is not familiar with the social networking Web site, which recently crossed the 200 million user threshold. Facebook is estimated to be worth $15 billion after Microsoft bought 1.6 percent stock in the company for $240 million.

Arie Hasit, 26, witnessed the birth of Facebook. He shared the same apartment as Mark Zuckerberg, the site's founder, joined the same college fraternity, and witnessed first-hand the company's initial climb from a dormitory start-up to a dominant mega-monstrosity on the Web.

Hasit grew up in Philadelphia. Since he was young, he dreamed of immigrating to Israel, which he did two years ago. Today he is serving in the Israel Defense Forces Spokespersons Unit. He chose to enlist for a year-and-a-half rather than the six months which are required of new immigrants in his age bracket. Israel is not foreign to him.

"Every summer I was in Jewish summer camp in the U.S. From time to time I would visit Israel."

After completing high school at age 18, he enrolled at Harvard University, where he studied the history of the Land of Israel. "I thought this would make it easier for me after I would get to Israel," Hasit said. "My parents actually thought I should learned computers so that I would work in high-tech when I got here."

Hasit focused his studies on the hip-hop genre in Israel, a subject which would become the topic of his thesis. He met Mark Zuckerberg in 2002 after they had joined the same fraternity which primarily concentrated on activities within the Jewish community.

"We ate Shabbat dinner together," Hasit said. "Every year we raised money for charities in Israel. Mark was one of the members of the fraternity, like many other Jewish students at Harvard."

Hasit, who wears a skullcap, says the 25-year-old Zuckerberg feels an affinity with Judaism. "He fasts on Yom Kippur," Hasit says of Zuckerberg. "Sometimes he would come to the Hillel House, a Jewish organization that ran various activities."

Hasit and Zuckerberg struck up a friendship, though they were not the closest of friends. They later lived together in the college dorms.

"Mark just happened to live in the apartment where I lived in the dorms," Hasit said. "He was in one room while I was in the other. This was a large apartment, we were seven students crammed into five bedrooms. We saw each other every day for a number of hours. When Mark moved into the dorms I was already in my third year while he was in his second year."

Hasit says that Zuckerberg decided one day to build a Web site that would serve as a utility for students at Harvard. "He built the site for fun," Hasit says. "We had books called Face Books, which included the names and pictures of everyone who lived in the student dorms. At first, he built a site and placed two pictures, or pictures of two males and two females. Visitors to the site had to choose who was 'hotter' and according to the votes there would be a ranking."

"He only ranked people who received the most votes for being good looking, not everybody," Hasit said. "There were about 1,000 people in all. Within four, five hours the site became so popular that at one point it became impossible to surf the Web on Harvard's Internet server. This was on a Sunday in October 2003."

"The next day, the head of the university denied Zuckerberg access to the Internet. People complained that Mark used their pictures without permission. He apologized and ultimately the university decided not to expel him even though there were columns in the campus newspaper that argued that what he did was completely improper."

Zuckerberg's stunt came at a time when students were appealing to the university to develop a Web site that would include the pictures and contact details of students in dorms. Now they feared that the Zuckerberg episode would compel the administration to shelve the idea.

"Mark heard these pleas and decided that if the university won't do something about it, he will, and he would build a site that would be even better than what the university had planned," Hasit said. "Before founding Facebook, he built the site Course Match which allowed students to find out who among those living in the same dorm are taking what courses, so that they could form study groups."

Zuckerberg started developing Facebook from his modest dorm room. Every visitor who registered at the site received a serial number. The first, second, and third user who registered took up dummy pages. The fourth user was Zuckerberg himself.

The fifth user is Chris Hughes, a co-founder of Facebook who also served as the company's spokesperson. Dustin Moskovitz, the third part of the site's founding triumvirate, occupies the sixth user spot. Moskovitz led the technical staff at Facebook before quitting the company to found a start-up in 2008.

Hasit's is the seventh registered user, which in practice makes him the fourth real user to log into Facebook. "Often people ask me how I became the fourth user. Sometimes I tell them."

"Mark came to me on the day he built Facebook, and he said to me, 'Arie, I built this site. I want you to sign up.' And that is how I signed up to Facebook. I put a favorite quote of mine in the profile. I specified my favorite books, which courses I take at Harvard. I uploaded one picture to the profile. There was no Wall. There was no News Feed. There weren't too many things in Facebook, which only began its lifespan on the Web.

"Initially Zuckerberg asked a small group of people to sign up to Facebook. At a certain point he told us to start inviting friends, and that is what we did on the first and second day which the site went up on the Web. We could only invite students enrolled at Harvard. In fact, if you did not have a Harvard e-mail address you could not sign into Facebook. At first, dozens of Harvard students registered. The numbers then reached the hundreds, and by the fourth day it had already reached the thousands. People were very enthusiastic about the site. It enabled them to know who took what courses and to meet new people. It conquered Harvard. In less than a week, some 4,000 students signed up for Facebook."

Hasit recalls how Zuckerberg spent hours in front of the computer. "He studied computers and psychology," Hasit said. "Despite the fact that he developed Facebook, he continued his studies as per usual. His grades were okay. He was even in a relationship with a girlfriend. During Facebook's initial days, the walls in his room were filled with graphs and charts which showed how many people joined on a daily basis, who used what application, and who has the most friends."

"After a few weeks, he decided to open up Facebook to another university. He had two friends, one at Stanford and the other at Dartmouth, whom he asked to promote the site there. He also asked for help from his ex-girlfriend who was a student at Dartmouth."

Facebook quickly attracted a following in other leading universities. "Every user specified which university he belonged to, and that was how he kept in touch with other students at the university in which he studied, but all the networks were under one Web site."

"The graphs and charts in his room became graphs and charts which included statistics from all the universities. At one point he received requests from students at other universities who were not in Facebook to open the site to them as well."