Preparing my Libraries orientation for graduate computer science students, and found this fascinating article on ACM Queue vol. 1, no. 4 - June 2003 - "How Much Storage is Enough?" : "In 1999, the world produced about 1.5 exabytes of storable content (1018 bytes). This is 1.5 billion gigabytes, and is equivalent to about 250 megabytes for every man, woman, and child on earth. Printed documents of all kinds make up only .003 percent of the total. Magnetic storage is by far the largest medium for storing information and is the most rapidly growing, with shipped hard-drive capacity doubling every year. Magnetic storage is rapidly becoming the universal medium for information storage...Although the social impact of the Web has been phenomenal, about 500 times as much e-mail is being produced per year than Web pages. It appears that about 610 billion e-mails are sent per year, compared with 2.1 billion static Web pages. Even the yearly flow of Usenet news is more than three times the stock of Web pages. As Andrew Odlyzko puts it, "Communication, not content, is the killer app." "