FaceBook Phenomenon

At this day Facebook still favorite for social network site. This phenomenon really surprise us. Why facebook be favorite site? as we know, at this time many social network site that already have first when compared to facebook. But why the site is less sound echo?
The same cases like google, where at the time many search engines that have been there first. but now google appears defeated all, which to this day remains the number one for search engine is google.
Questions that often appear in fact why the latter appears more easily in the top right of appeal has been? Analysis!!