I'm sure you've heard the modern-life truism that the Library of Congress has less trouble preserving their "old-time" documents and data from hundreds of years ago, but are terrified about all the varying ways they can lose digital, CD/DVD, and tape-recorded data from the last 50 years. The sad truth of it is, modern data storage is handled much the same way as a fast-food restaurant is built: We only expect it to last for 5 or 10 years.
I went out to dinner with a friend of mine whose specialty is JPG compression, storage and retrieval, and he terrified me with stories of massive data loss.
Which is why I'm so excited about Apple's Time Capsule. The ability to be constantly backing up my data via Wifi is a brilliant idea. Taken with offsite storage (I use Apple's .Mac iDisk, but there are plenty of good options), and a Lacie external drive...I think my thousands of scanned Sheldon toons are finally getting the redundancy I should've had a long time ago. So hopefully they'll last a little longer than 5 to 10 years.
...But Abraham Lincoln's hand-written letters will still outlast all of them.
And maybe that's OK.