The reason that "email" will never die is that the limitations of the human mind compel user interface designers to employ the principle of least surprise and t

The reason that "email" will never die is that the limitations of the human mind compel user interface designers to employ the principle of least surprise and to extend existing metaphors slowly. In practice, many people are using "email" which runs on internal Exchange systems and is accessed using Outlook or web applications. When I send an email via Gmail on my "phone" (Which is as much a camera that can make calls as it is a telephone that can take pictures - the only reason we use one metaphor and not the other is path dependence) to someone else using Gmail, I am "sending them an email" without using the protocols that the original implementers of email had in mind. It's the same reason that we can call a web site a "page" or a "document" despite the fact that a modern web site is actually several programs running insider your browser (flash, custom JS, HTML rendering) working together with programs running on a number of different servers. That's nothing like a paper document, but we use the metaphor because it's been extended a little bit at a time.