I started thinking about how Twitter is very much a social networking tool for adults that is similar in some ways to MSN chat, and in other ways is like email. This thinking prompted me to a thought experiment comparing the adoption of tools used for communication:
(Creative Commons Licensed by Rodd Lucier)
While it's dangerous to generalize, I'm coming to a fearful discovery: "It's not that education fails to take advantage of technology; it's that education fails to take advantage of most forms of communication that cross time & space."
Common practice seems to be in the here and now, whether speaking to people who are present; or writing for people who are present. Although there are many exemplary learning experiences taking advantage of communications technologies, these exemplars are far less common than so-called 'traditional' learning experiences.
More detailed thinking on this topic is available on the Teacher 2.0 Podcast: Unharnessed Communications Technologies.