I joined Facebook because everyone I knew in college had a Facebook account. There was no culturally charged avoidance factor for my MySpace account. MySpace was ugly and felt like a spam website (and when I started receiving fake requests for friendship from random good looking women, it was a spam website) whereas Facebook was clean, usable, another good reason why I switched. The primary motivating factor was simple: "What are my friends using?" I now have a pretty substantial network of friends on Facebook and don't have the /luxury/ of switching. THIS is the issue. You cannot migrate all of your data and still interact with your network of friends on MySpace when you switch to Facebook, so you don't switch. The digital ghetto exists not because of choices made by users, but because of the lack of choices users have once they're effectively locked into a service. I'm sure you could craft a clever analogy to show how this is just like white flight as well, but it just doesn't make sense IMO.

By the same logic we could say that all the hotmail users live in a "digital ghetto", and all of the white upper class folks got the hell out of dodge and went over to that sweet homogenous GMail service where everyone has a PhD. It's ridiculous.

There's no barrier to entry, but there is a barrier to /exit/.