P2P facilitates the rise of unique communities where people can find one another regardless of distance, country, and culture.

Unlike blogs and discussion groups, the medium is not text but multimedia. The first P2P groups centered around music. PC's easily converted live and recorded songs to digital files, enabling both professionals and amateurs to comment, imitate, and collaborate.

Today the medium is video, enabled by cell phones and cameras that record and send with a click. Post a video and you can attract many thousands of viewers who respond in kind with their own video, whether it's a comment on your video or their own viewpoint, how to guide, mash-up, or work of art.

The New York Times ran an excellent piece called The Many Tribes of YouTube. The article covers the rise of several communities, including senior from personal rants to complete oral histories, time-lapse painting that shares that art form much like technology did for musicians a decade ago. My favorite is parkour, the sport and art of extreme gymnastics where athletes scale buildings with amazing dexterity and grace.