For at least a century, terms like 'avant-garde' and 'cutting edge' have been associated with cultural products that lie outside the mainstream. That is, the cutting edge is usually something that most people aren't interested in. By the time it becomes mainstream―in other words, by the time the majority of people come to know about or appreciate it―the cultural product in question isn't cutting edge anymore. This is true in almost every medium, including painting and other visual arts, film, music, and literature. The things that have real, lasting cultural importance, are, at first, adopted and endorsed only by a select few.
Of course, the question that is raised by these considerations―what causes cultural products to rise from obscurity to cultural importance, and eventually, to enter the mainstream? There is an argument to be made that the tastes and whims of influential people and institutions have as much to do with this process as the content of art and media itself. For example, Jean-Michel Basquiat, one of the most famous 'outsider artists' in history, rose from obscurity to massive prominence largely thanks to the influence of Andy Warhol and his associates.
The point is even more strikingly made in the example of music. Which musicians become famous has historically been almost entirely up to the record companies. Much mainstream pop and rock music is tailor-made by large record companies to have a high profile and high sales from the start, with little thought to artistic expression or cultural importance. More experimental musicians, however, have to get lucky with record companies in much the same way. Out of 10 culturally relevant musicians, one might get a decent deal with an independent record company, without which, their music would never be heard. Which one of the 10 gets this exposure is, perhaps, the luck of the draw. If the indie band goes on to become hugely influential to future musicians, the role that fortune played in this state of affairs ought not to be overlooked.
Who Decides What's Important?
To some extent, then, the avant-garde is determined by those who are already part of the mainstream. Record companies, production companies, established artists, and art galleries, all have an important say in what's cutting edge, so the distinction between the avant-garde and popular opinion is perhaps not so clear cut. In order for creative endeavors to have an effect on culture, someone with the power to impact culture has to get involved.
Historically, small-scale promotion of new, exciting media has been important. When a new band or independent filmmaker arises and appeals to trendsetters, these trendsetters spread the word in a number of ways, and this 'underground' promotion helps avant-garde artists along the path toward cultural relevance and mass appeal. In the past, if something gained enough of an audience to be noticed by larger institutions, it had as good as succeeded in 'breaking through'. Today, however, it is becoming less and less clear what a breakthrough act is, what the mainstream is, and whether the concept of mainstream versus avant-garde media retains any relevance at all.
Becoming Famous Online
The most obvious example of the cultural shift that has taken place over the past decades can be seen in the way the Internet has affected the spread of cultural information and media. In the past, a new pop group had to start locally, growing in importance via word of mouth and bootlegging, eventually earning the attention of a large record company and growing in popularity (and, often, decreasing in cultural importance) from there. Now, this process has been almost completely overtaken by online word of mouth. A new band, instead of distributing demo tapes to record companies and radio stations, can put its music on the Internet for all to hear. People anywhere in the world can listen to and respond to the band's music, vastly increasing the potential increase in popularity via word-of-mouth. Thus, culturally important, experimental musicians can become widely known before they have been noticed by the mainstream. It hardly needs to be said that this places far more importance on the content of the media being distributed online. The support of an established artist is no longer necessary for new artists to become successful. Instead of a cultural hegemony of the influential, we now have a situation where, thanks to technology, culture is becoming more democratic.
The Democratization of Culture
The democratization of culture is, perhaps, killing what was once known as the mainstream. Because institutionalized support is irrelevant, a musician, artist, or even (though to a lesser extent) a filmmaker can become successful and well-known without ever becoming famous in the traditional sense of the word. Instead of culturally important media products rising to the mainstream after slowly gaining acceptance in avant-garde communities, many media communities remain avant-garde. Not only does this eradicate the idea of a strong distinction between cultural relevance and mainstream prominence, it calls into question the future of the mainstream. With a more democratic approach toward culture, the cultural hegemony that established the mainstream in the first place may no longer be necessary.