Published Jan 1, 2007 8:00 AM

21. Hooked Up

What: Metcalfe's Law (social networking)

Who: Inventor Robert Metcalfe

Impact: OK, here is the breakthrough in science-speak: Metcalfe's Law states that the value of a telecommunications network is proportional to the square of the number of users in the system. That's how Robert Metcalfe, the inventor of Ethernet, the most famous local-area computer-networking standard, first formulated it when he was working at Xerox PARC in Palo Alto in the mid-1970s. In layman's terms (that is, English), this irresistible techno-cultural force is known by a far less daunting description: social networking. As the Internet has been, it is beginning to look like mere preparation for an even bigger tech wave: online communities. A whole new generation of entrepreneurs is taking Metcalfe's Law to heart and creating Web-based structures that link together people of common interests into ever more valuable networks: MySpace, Facebook, YouTube, LinkedIn, craigslist … hundreds now, and more to come. Value? How about $1.6 billion, the price paid by Google to purchase YouTube.

Eureka moment: When Metcalfe first pointed out that his equation might have some real-world value, few people noticed. His is a particularly maverick genius, half a serious technology entrepreneur (he founded 3Com Corp.) and half a fun-loving iconoclast. Thanks to never being taken quite seriously, Metcalfe spent many years largely uncredited for his greatest discovery. Even now, when it seems every other new high-tech business plan is built upon his Law, Metcalfe has moved from Silicon Valley to Maine, where he is more likely to be found in a local diner than in a laboratory.

— Michael S. Malone