More and more theses and other scholarly materials are being made available only in electronic form. This has been a concern of mine since the time a few years ago when I found that I had an electronic file that no one on our campus could open. While written texts can be preserved for hundreds or thousands of years "electronic records that are not moved out of obsolete hardware and software environments are very likely to die with them." (David Bearman, D-Lib Magazine, April 1999, vol. 5, #4) Bearman recommends the "migration (of) electronic records systematically before they become inaccessible, so that they are always available to current generations of software and hardware." Unfortunately, I have not been doing this and I don't know of anyone who has.
I recently heard a military historian voice concern that David Petraeus' emails would not be preserved like Eisenhower's diaries were.