Friendster started 2 years earlier than facebook in 2002, and facebook was a closed network then, only for college students, they only opened up to the public in late 2006.

Facebook is wildly popular in the Western countries especially among the college and undergraduate students, since it was targeted at them at first. If you have any friends studying in uni overseas chances are they are on facebook.

The reason it became so popular is i guess it's clutter-free design, it's clean and sleek. Most important of all, it really allows you to connect with people you know, unlike myspace or friendster where you just randomly add people you don't know to boost friends count. IMO the most important feature in facebook is its news feed, amazing how the thread starter missed out in the 1st post, it really allows you to keep yourself up to date and know what's going on around your social circle.

Sadly after saying all its amazing features of connecting with people, i've got no one to socialize with....