So Slate has an article entitled The Death of E-Mail about the younger generation in the US abandoning email. My colleague and good friend Jim Hickey made the same observation to me month or two ago. For his sons, email is how you submit papers to your teachers. It's a formal means of communication, much like snail mail is to me.
Actually, Facebook messaging is replacing email even for me for a certain class of communication. And just in the last 24 hours I've received a number of messages (about my MINI purchase) from old friends I haven't seen in years (more than 20 years in one case) who I wouldn't even be in touch with at all if it wasn't for things like Facebook. Even between me and my colleagues, non-work communication is done more over Facebook than email now.