It seems that Facebook has truly relegated MySpace to the wilderness. Social Networking essentially means Facebook at this point. MySpace is an afterthought for the great majority of people.
One of Facebook's important strategic decisions was to early on promote Facebook applications, that gave users the ability to perform a multitude of activities that was in a constant state of growth, but that didn't require growing Facebook resources. All they had to do was oversee and manage the process.
There was an article in Naperville Sun-Times today that explored the concept of addiction to Facebook. There are no similar discussions surrounding MySpace, in part because the activities on MySpace are still fairly limited.
One of the better quotes from the article:
"Oswego High School freshman Sara Rozhon told me she spends about two hours a day on Facebook. 'I'm addicted. (Without Facebook), I probably would have straight A's in all of my classes, and more of a life.' Rozhon does admit, 'I honestly think that without the distraction, my life would be easier.'"