From John’s Observer column:
I can look at someone’s PC and generally infer from the pattern of folders and files on the disk when they first started using computers. The clue is that older users tend to have orderly filing habits. They also tend to cull old or temporary files, and are more wary of accepting large downloads. Why? Because when they first started using computers, disk space was scarce (and therefore expensive and precious); the same applied to connection bandwidth.