1. Incomplete copies with missing dependencies. 2. Old software and their file formats with a poor virtualization story. 3. Poor cataloging. 4. Obsolete physical interfaces, file systems, etc. 5. Long-term cold storage on media neither proven nor marketed for the task.
Managing archives is just a cost center until it isn't, and it's hard to predict what will have value. The worst part of this is that TFA discusses mostly music industry materials. Outside parties and the public would have a huge interest in preserving all this, but of course it's impossible. All private, proprietary, copyrighted, and likely doomed to be lost one way or another.
Oh well.