Memory is a fickle thing. As far as my brain is concerned, I didn't exist before age three. Remembering four or five is easier, but there are holes. Thankfully, all it takes are some voyeuristic navigation tools to fill them.

Before there was random access memory, there was delay line memory. It was random in a different sense; it involved turning electrical pulses into sound waves, sending them through long tubes of mercury, and re-electrifying them at the other end.

You're looking at a woman who resembles your mother. She moves and talks like your mother, and she's even dressed the same as your mother. In fact, she is your mother. But you're absolutely certain that she's an imposter.

Imagine a format that lies somewhere between photos and video, and a device that takes that format automatically, without you having to click a button. Microsoft's SenseCam is a prototype that hangs around your neck, lifecasting everything you see.

All this talk about preserving digital legacies got me thinking: What about the bits we don't want to leave behind? Y'know, the risqué material? Don't pretend you don't know what I'm talking about.

Just a few years ago there were no virtual social networks, no synchronized address books, and no smartphones. But people had social networks and phones, and they had to memorize and organize thousands of contacts. Or have a Rolodex.

It seems like something out of a movie (and hey, it is), but there's some scientific evidence that we actually carry the memories of our ancestors with us in our genetic code. Apologies in advance to my hypothetical descendants.

We say pictures can't replace memories, but when Halley's Comet last swooped across the sky, many of us were too young to care. Our next chance to see it—about 50 years from now—will be probably be our last.

Before David Carr was my favorite NY Times columnist, he was an asshole.

So your hard drive just died, and you didn't back it up. I'm so, so sorry. You can expect to go through the following five stages once you discover that all of your photos, files and music are gone forever.