Ideas come and ideas go. Sometimes they blaze hot and move fast through media spaces like print, television, movies, and pop music. Or they burst onto the Internet and travel the gossip hotline of the blogosphere. When they acquire an effortless momentum of their own, keen observers talk about memeflow. Look, look, it's the next big thing: portals, page rank, peer-to-peer, blogs, RSS, social software, tags. The beat goes on.

But a meme is more than a passing fancy; it's a self-replicating, widely adopted idea, an idea with legs. Memes are of the moment, but their mission is to evolve and endure.

The notion of memes borrows from the study of genes and genetic evolution. Genes replicate, evolve, and spread biologically, while memes are transmitted by human communication.

Over the last few months, you may have noticed the emergence of a new meme: The Long Tail.

The long tail is a familiar statistical truth: Small, everyday events are extremely common, and big, momentous events (from huge blockbusters to great catastrophes) are rarities that attract attention. This phenomenon occurs in the natural world (there are many seismic blips and few major earthquakes) and in the human realm. You can see it in the distribution of wealth (there are very few billionaires) or population (there are very few mega-cities) or popular search queries. Or, you can see it in WordCount, Jonathan Harris's interactive widget that displays the frequencies of word use on the long tail of our language.

Back in October, Wired editor Chris Anderson authored a thought-provoking and influential article titled The Long Tail, and created a companion Long Tail blog, which he describes as "a public diary on the way to a book." In recent years, scientists and statisticians have applied Zipf�s law, power laws, and Pareto distributions (the old 80/20) to analyze and explore long-tail statistical phenomena on the Internet and elsewhere. But Anderson's riff takes it one step further.

Anderson explores how the Internet has changed the laws of distribution and the rules of the market. The barriers of time and geography are down, so is the cost of storage. The limitless shelf space of online commerce and the availability of powerful search engines and free or cheap publishing and communication tools (email, groups, message boards, instant messenger, groups, and weblogs) create new economic, social, and cultural opportunities and new freedom of choice.

Suddenly, the mainstream is not the only stream. There's room now for babbling brooks, crooked creeks, and tributaries where trends pick up momentum before they flow downstream. There's an audience for many voices --for the eclectic and the unpopular: little blogs and the micro-communities that cluster round them, small-press books on oddball topics, indie music, and arcane genre movies for niche audiences. Wikipedians edit thousands of articles on hundreds of thousands of topics. Breadth of content thrives in environments that are collaborative, distributed, bottom-up, and driven as much by passion as by profit.

In a comment to one of Anderson's blog posts soliciting definitions for the Long Tail, an Amazon employee described the marketplace sea change this way, "We sold more books today that didn't sell at all yesterday than we sold today of all the books that did sell yesterday."

It's no longer necessary to focus myopically on bestsellers and mass appeal, that's the message. Devoted enthusiasts, professional amateurs (pro-ams), and like-minded people find each other to create communities of interest, spread influence, and share recommendations. Thousands of RSS feeds bloom, and anyone, anywhere can find them, mix them, and add them to My Yahoo!. On Yahoo! Shopping (or Amazon or eBay), merchants add their goods to a global catalog connecting consumers to any title, any product, any brand. On Overture, merchants buy keywords that drive business to an "abundance of niches."

There are plenty of pilgrims on the long tail trail. To travel this road wisely and well, we all need long-tail tools that support self-expression, personalized search, recommendations, and trust. Anderson's vision shows us a horizon as vast and limitless and rich with possibility as the long tail itself.

What aspect of the Long Tail makes your tail wag? As always, we'd love to hear your thoughts.

Havi Hoffman
Yahoo! Editorial