I have just started to follow this thread, so forgive me if this is a repeat. I have found Facebook to have taken off recently in the Toronto community. The huge size of the Toronto FB community is now well known: http://blog.facebook.com/blog.php?post=2398302130 I bridge two communities -- academic and interactive private sector. The interactive types scorn myspace because of its horrible UX. Facebook however is widely praised for its innovative interface, its use of latest fast-loading front end coding (e.g., DHTML), and its recent opening of its API. I find interaction designers frequently use Facebook as an example and an exemplar of good UX. Now for the scholarly types, this community seems to be a bit more fragmented. I know many of these people who have accounts on myspace and even friendster, in addition to Facebook. I personally have an inactive friendster account that never ceases to amaze me when I get notices that someone actually was there. These are slowly dribbling off. I also find it interesting that NONE of my academic friends use Linkedin, but my private sector contacts consider it de rigeur. If we are to adapt Goffman's notion of "the front," I believe each "place" has its own "scripts" that are attractive to some and unpalatable to others. Perhaps the linkedin front is too "business-y" for sociologists.