There is rarity, certainly. And encryption and access control. But nothing so esoteric that it cannot be realized. All the grimoires are in print, and corporate email is a hack away. We need not mourn the burning of the library of Alexandria because we have far surpassed it and, while ephemeral in some ways, the information is so well distributed as to be presumably indestructible.
But electronic memory decays if not constantly refreshed. So too does the substrate of our distributed electric memory, where fickleness and technology change obsolete entire media.
It is a paradox: Yes, I can read the Dead Sea Scrolls online. But can I still read anything written in WordPerfect?
With the rarest and most bizarre texts scanned and stored, the most esoteric knowledge in the information age is knowledge about information itself. Hacking is as close as we have to a modern magical tradition. And next to content creation, the most important task for the wired mind is content curation.
The fact is that, cranky anti-hipsterism aside, it actually is curation, which is not only "an act performed by people with PhDs in art history." The "New Aesthetic", after all (which isn't so new), isn't au courant by way of the Guggenheim, but because of the thousands of twittering thumbs of the nerd horde at SXSW.
We rely on some curators for certain kinds of feed: Laughing Squid, Brainpickings, even the self-consciously trivial Gawker flotilla. But we also make ever more use of our own curatorial technologies: not just our blogs and twitter accounts but Pinboard, Pinterest, Gimmebar, Tumblr and even (for those whom code is content) Sourceforge. We determine what is kept and elaborated on, and what is discarded and allowed to decay.
And by using these filters, not only of our direct choice but of our selected curators (and so making metachoices), we determine what shapes us. Our information diet is almost as much of our experience as any sensory data, and arguably has deeper effects on our psyche.
We think of ourselves as pragmatic, as grounded in the real. But everything you think you know about anything not in the range of your senses comes through media, not experience. What you accept as true is dependent on what media you accept as reliable.
We are as librarians, and might as well get good at it.