This century's last great trend was noted by acute observers in 1996, yet most people failed to appreciate it. While business gurus were proclaiming the new dominance of creativity and innovation over mere production, the growing ease with which information was transmitted and reproduced made it harder for creators to profit from their creations. Nowadays, if you develop a marvelous piece of software, everyone will have downloaded a free copy from the Net the next day. If you record a magnificent concert, bootleg CD's will be sold in Shanghai next week. If you produce a wonderful film, high-quality videos will be available in Mexico City next month.

How, then, could creativity be made to pay? The answer was already becoming apparent a century ago: creations must make money indirectly by promoting sales of something else. Just as auto makers used to sponsor grand prix racers to spice up the image of their cars, computer manufacturers now sponsor hotshot software designers to build brand recognition for their hardware. The same is true for individuals. The royalties that the Four Sopranos earn from their recordings are surprisingly small; the recordings mainly serve as advertisements for their concerts. The fans attend these concerts not to appreciate the music (they can do that far better at home), but for the experience of seeing their idols in person. In short, instead of becoming a knowledge economy we became a celebrity economy.

Luckily, the same technology that has made it possible to capitalize directly on knowledge has also created many more opportunities for celebrity. The 500-channel world is a place of many subcultures, each with its own heroes. Still, the celebrity economy has been hard on people -- especially for those with a scholarly bent. A century ago, it was actually possible to make a living as a more or less pure scholar. Now if you want to devote yourself to scholarship, there are only three choices. Like Charles Darwin, you can be born rich. Like Alfred Wallace, the less-fortunate co-discoverer of evolution, you can make your living doing something else and pursue research as a hobby. Or, like many 19th-century scientists, you can try to cash in on a scholarly reputation by going on the lecture circuit.

Endless channels of media allow for more celebrities, but to smaller audiences. In order to make money from media, celebrities must sell more than their works. Their works must serve as advertisements for something else, like paid performances or lectures.

Asymmetric attention is the key to another important concept, celebrity. Being famous means that a lot of people pay attention to you--after all, by definition it is famous people who appear on the cover of magazines, which are purchased because lots of people want to know what\'s happening with their favorite celebrities. But the celebrity doesn\'t, for the the most part, pay any attention to the fans (at least, not individually). Asymmetric attention ties in Twitter allows people like Oprah Winfrey to have millions of fans, just like she does on television, without needing to pay attention to all or even any of them. In short, asymmetric attention allows Twitter to be an extension of other forms of mass media as well as a conversational medium.

Likewise, the existence of symmetry is informative as well. If two people follow each other, then they are each paying attention to one another, and each is receiving information from the other. This is powerful stuff, even more so if each has sent @replies to the other, because this is better evidence of a strong social tie between them. Note that the exchange of @replies makes a symmetric connection out of two asymmetric ties.

Twitter provides for asymmetric connections, where individuals follow others, making the people who don\'t follow back are celebrities; however, the system has been hacked with @replies, which make asymmetric connections symmetrical.