I often think about the amount of data that's been lost already due to changing file formats and stuff.
Leaping off in a different direction, did you ever read "A Fire Upon The Deep" by Vernor Vinge? This starts with a human expedition at the outer edge of the galaxy investigating a five-billion-year-old data archive that offers the possibility of unimaginable riches... but it also offers unimaginable dangers...
There will be a 30 - 50 year gap for future historians to contemplate. Somewhere, the masses started creating and storing everything digitally. Many of those folks don't know how to manage all of life's data (who does?), especially through multiple generations of computers. Much of this will be lost to history.
At some point, everything will live online - that permanence - and most of that should stay forever do to professionals managing the transition.
We're a good way there, but not quite yet. File formats will change. Someday Jpeg and word files may not be readable and it won't matter where it's stored. Once file formats stabilize, or someone developed a way to covert formats en mass, the gap will be over.
Nah ... I did consider this when I did the first post deep in the mists of time -- but if you visit the site you'll see that it's legit -- they boast about this prank and how many folks they have visiting -- plus the rest of the site is devoted to cell-phone relayed adverts.
Also, like I say above, you don't have to give a real cellphone number...
I don't think that we have begun to grasp the unintended consequences of the permanence of the internet. Information will not go away, and when it may pop up again we have no idea, no control over what other information it may be associalted.
In time, ths information will span generations, telescoping history into a mashup, and our ideas of old versus new, fashionable versus uncool, will become uncontrolled and anarchic.
Ad we won't notice it happening...