Encouraged by proliferating media choices, the traditional American melting pot is giving way to finely segmented affinity groups based on values and interests, rather than demographics. In turn, these psychographic clusters are becoming identifiable market segments.

Let's examine the facts and their implications:

Human beings are social animals. Unlike tigers or grizzly bears, we aren't solitary creatures seeking to live and work alone. From prehistoric times, we clustered together in groups or tribes, with shared values and beliefs. These have usually been defined by geography, religion, and family ties.

But more and more, we're choosing our own groups or tribes based on mutual interests. Consider those who ride Harley-Davidson motorcycles, the thousands who gather each year in the desert near Reno, Nevada for the annual festival known as "Burning Man," or the hundreds of thousands of men who turn out each year for "Promise Keepers" events across the U.S.

People like to be part of well-defined social groups. This is why we join country clubs, fraternities and sororities, and civic organizations. Churches, civic organizations, and sports teams are primarily geographically driven because, until recently, most people have had limited chances to join social groups that were not based in their neighborhoods.

But now, thanks to modern telecommunications and transportation, we are no longer limited to geography-based groupings. The Internet enables us to form new communities. We can chat on the telephone to a fellow group member across the country for $1. And low-cost travel makes it possible for the new interest-based groups to assemble relatively easily.

As a result, highly targeted groups are now being assembled from around the world. Just as important, multi-culturalism and tolerance have made people more willing and able to explore new possibilities and interests. And, just as Marshall McLuhan predicted back in the 1970s, these new affiliations based on interests are likely to take the place of traditional groupings based on kinship, religion, and geography.

Specialized media not only sprouted up to support communities of interest, but they help mold, define, and reinforce the values and perspectives of these communities. And technology is making it possible to target media cost-effectively, including on-line bulletin...