In this day of mass storage and internet we take for granted information. What we miss is the loss of information that occurs around us with great frequency and quantity.
We are approaching the last flights of the space shuttles and one of the things I bemoan is that when the shuttles stop flying forever all of the information that goes into making, testing and flying the shuttle will be lost just like the earlier programs like Apollo, Gemini and Mercury. It came to pass that when NASA and their commercial vendors started down the path Constellation and Orion it was discovered that what had been done before was forgotten and mostly lost. It became a task of researching how did they do that!
How does this happen, simple really. NASA contracts to vendors and to build and do research and the vendors maintain files. If the programs files the files are kept and are retained for some period afterwards. This is both normal and typical. Later after the project has ended the retention period times out usually after 7-20 years and guess what, those files being bulky and requiring floor space are simply disposed of assuming a fire or flood has not destroyed then before then. Often this also applied to electronic files as well. If the media is not destroyed it goes moribund because the technology to read it has gone by or the computers of the time that had the devices to read it have also gone by. This is very common for the pre-IBM PC and internet era.
If you take a moment to read the blogroll for the Apollo Guidance Computer You will say one persons work to discover how did they do that and how much was not findable any more.
Hopefully this painful event may not happen to the shuttle as it's lifespan brought it into the modern PC era. However there are many files and details that could be lost just like how we got to the moon.
In this age of information being a commodity of value this one hopes that some bits of it haven't become so low in value as to be reduced to simply "We used to know how but, it's forgotten.".
Something to ponder.