Every new feature Facebook introduced has already been done by someone else. When it started, it was a simple clean website, and that ease of use attracted the initial users. Then Facebook was opened for apps, and there was a flood of zombie/vampire apps, and widgets to customize your page with. Like most geeks, I got sick of those years earlier, having visited enough PHPnuke-based portals and linkspam-based games.

But for many people Facebook was an introduction to the things you could do online. It was a structured, gradual, hand-holding introduction, which is what I think made it work.