Music has always been a way for people to communicate and create an identity. From the traditional and world music of tribes and alike to the modern multitude of genres and subgenres, many closely associated with social groups.
In a modern perspective, I think we sometimes forget about this, almost instinctive, way people want to identify themselves using music (among other things). One company and service which do promote using music as part of an identifier is Last.fm. Basically, you give Last.fm information on when and what you are listening to, they then makes this information available in a online community (or more precisely; the whole world wide web) in a way that makes your profile as an individual clearer and better defined. Last.fm also helps finding other people in the world sharing the same taste in music, and probably also share more stuff on other levels.
May it be connecting people by means of music, interests, taste of fine arts, ethic groups, business branches, schools or sports the effect is the same: Increased definition of the individual. People tend to being drawn to social groups, especially in early ages (teenages).
Music becomes a more important method of definition as the modern society blurs the borders of traditional groups like ethicality and alike. People travel all over the world and business do the same thing, spreading across nations and continent boundaries.
I would like to see more focus towards social identification of the individual, in the music-biased services of today and tomorrow. Easy access to technologies like web services/APIs and feeds can further enable expansion of the individuals’ social presence.