E-mail seems to truly have died out as a preferred communication method online. Most of us have e-mail accounts but few of us use them to write messages to friends or family or to carry on conversations. Rather, our inboxes are simply the place for our various web registrations, spam, and maybe even the occasional "notes to self". But how did this happen? How did such a web staple, right up there with IRC and Usenet, come to such a dwindled low?

This inbox is alluring isn't it? All that fresh e-mail awaits you.
I thought about this for some time and came to the conclusion that it actually didn't. I've decided that the end of e-mail is more an illusion wrought by a fundamental change in form and process, but, in effect, we still use it or at least use it most appropriately.
Consider for a moment that the initial spike in e-mail use that defined its era was more about the public's fascination with a new instrument that allowed one to convey thoughts and ideas eyeball-to-eyeball for, like, the first time ever. With electronic mail people could skip letter writing, the process of sending them, and the subsequent delay in any response. The only thing that came close before e-mail was the telephone or its clunky cousin the fax machine. There's a certain amount of enthusiastic overshoot that comes with breaking barriers such that e-mail did for us, but it wanes relatively quick once the first rush of all the ideas that "need" to or "could" be shot to someone in a micro second, are. Imagine all that energy on a collective scale, not individual, and you get the idea. Once the ability to e-mail someone became the norm people retracted their interest and it all became less fun and perhaps more work.
That's as far as the genuine decay went because, in time, e-mail melted away into a dozen other vehicles that are even cooler. Yes we stopped e-mailing, but we didn't stop communicating electronically. The model of single inbox-to-inbox communication may play a smaller role in online chatter, but we still communicate online, and how.
Naturally Facebook comes to mind but even within Facebook we have to parse out examples to understand. Within Facbook there is, in fact, a dedicated inbox. There is also the less personal wall-to-wall communication, and by contrast, highly real-time instant messaging. All of this means that with less of a mass to communicate that e-mailing occurs in more deluded forms of quick comments and short message darts, all blasted as one-liners.
Look at it this way, if you've already shared a You Tube link, remarked on someone's Facebook post, shot them an instant message, and finally, queried them as to the next meetup via text messaging or perhaps some online calendar app; there is very little subject matter left to e-mail about. Granted all of this fragmentation is not as convenient as a single reference to our inboxes, but perhaps all of that in its totality would be overkill. In any event we don't seem to mind.
We don't dismiss the import of e-mail by a long shot. E-mail is the preferred communication protocol of most work places, though our bosses would like us to keep our thoughts concise enough and most of all scandal-free. As well, we all have an e-mail address if not several if only to allow for signing up to all the other e-mail killing services mentioned above. We still take pride in our custom filtering methods and our labels and folders, and we still yearn for the twinge of reward that comes when we spot a new message adorned by a friendly, familiar, from address. Even if we aren't nearly as inclined these days to furnish such messages ourselves.