Autoplay music, crappy css, and so on gave myspace a childish feel that people abandoned when they moved to the cleaner, better, facebook. I also remember facebook being the "better" thing, like how many see android as vs apple. We cheered for facebook beating myspace because facebook was new, was cool, and was different. Which is really odd, since I never really had a facebook or a myspace account.
I still think Facebook stuck because of Collegiate exclusivity and then proliferating among the 18-35 age group after that was dropped in like 06' -07' because of their friends in college. Then everyone else came.
It's interesting how MySpace lost the crown. They had the security of the network effect, but that was overcome by Facebook's collegiate-focused approach. Craigslist won't be toppled by another Craigslist. It will be toppled by a site that begins far more narrow in scope that can expand once it reaches a critical mass. I can't believe how many employees some of these sites take on. If you over-staff with engineers, you are going to over-engineer. If you over-staff with marketers, you are going to over-market. If you have too many employees, you need to make too much money. Venture capital funding is the same. It is a piper than needs to be paid.