Old ideas aren't the trendiest, but they're often the best. Take the example of Yahoo!, whose founders Jerry Yang and David Filo saw that despite the merits of search engines, the venerable concept of card catalog subject headings still had plenty of merit. By a process of reinvention, and without bothering to hire any actual librarians, Yang and Filo quickly proceeded to fortune and fame.

Or take the example of the proxy server. This is a concept that sounds trendy and cutting-edge, but its roots are also in dusty old library science. Remember in college when you first needed to check out a book housed in your university's locked stacks? Since you weren't allowed to go into this secured part of the library, a staff member acted as your proxy and retrieved the book for you.

All too often, of course, this process took longer than if you'd been able to go to the shelf and get the book yourself. But suppose that each time librarians retrieved a book for one student, they also made several copies, keeping them at the front desk for other users who requested the same title. The result would've been an ideal blend of fast service and airtight security.

This analogy explains the two main functions of a proxy server. First, the proxy server acts as an intermediary, helping users on a private network get information from the Internet when they need it, while ensuring that network security is maintained. Second,...