MySpace pretty much paved the way for Facebook. It was the experimental and kooky product that really got the ball rolling on social media, but was too weird to dominate. Then Facebook came in and, among other things, cut out all the crazy customization and provided a clean and consistent interface that had a much better chance of being used daily by a wide range of people.
Another thing Facebook did was start small and slowly roll out to more users. This is kind of antithetical to the ethos of "launch to the public ASAP, get those users!" By starting with a limited and already connected group of people (Harvard students), they were able to realize network effects with less users, and it very quickly integrated itself into their real social lives in a way MySpace hadn't. Being sort of "exclusive" also fueled initial interest among a set of valuable users that would become evangelists.
The customization thing was somehow thought to be really important. That was part of "Web 2.0". Customization is part of what killed Tribe, which "upgraded" and implemented customization badly. You could slide everything around. The user had to get panes and widgets to not overlap, then be careful never to slide anything again.
This is a classic programmer design error. Faced with an aesthetic decision, there's a tendency to punt and make it user-programmable.
I'd say rather than an error per se it's the classic tradeoff between the open "blank canvas" approach and the structured "walled garden" approach. One promotes user creativity and expression at the expense of cohesion, the other creates a consistent experience at the expense of freedom.
Initially when people come from myspace they were using it similar to myspace. Facebook was all about profile widgets, although they still fit a more consistent layout.
Another thing Facebook did was start small and slowly roll out to more users. This is kind of antithetical to the ethos of "launch to the public ASAP, get those users!" By starting with a limited and already connected group of people (Harvard students), they were able to realize network effects with less users, and it very quickly integrated itself into their real social lives in a way MySpace hadn't. Being sort of "exclusive" also fueled initial interest among a set of valuable users that would become evangelists.