Traditional media relies on a relatively few channels bombarding a captive audience with desirable advertising or publicity. In laymen's terms it could be called a honeypot approach where radio and television studios create compelling and entertaining content for a captive audience. At regular intervals that captive audience is made to watch an advertisement. The relatively few broadcasters competed to produce the most enticing programming that would draw as big and as diverse of an audience as possible.
The Growth of Cable
The growth of cable caused a multiplication of available channels which in turn led to a mass segmentation of the viewing markets. This segmentation meant that advertisers could better target audiences for advertising, albeit the reach for each particular cable channel decreased.
The Rise of DVRs
DVRs again chaned the ladscapt because viewers simply started skipping commercials. They still wanted to watch their programming but commercials were not reaching. This led advertisers to seek out and value events that were carried out live, like sporting evens, that were less likely to be recorded.
Subscription Based & On Demand
The rise of Subscription Based and On Demand programming again led to further dilution of advertising markets where customers payed a studio like Amazon or Netflix for an entire season of a show at once. This left advertisers out in the cold, with perhaps the exception of clever product placement within those shows: cars and other easily recognizable products.
While extreme changes were occurring within the television and radio markets, the internet was busy inventing social media, where people could assosicate. Facebook boasts 1.59 billion customers; Instragram, 400 million; Twitter 320 million; Google+, 300 million; Pintrest, 100 million; LinkedIn, 100 million. WIthout a doubt, these markets are massive.
Traditional advertising can work for social media where paid advertisements are delivered to audiences, but those advertisements are usually ignored. The true value of social media is memetics, where compelling advertisements are willingly progagated by people to other people -- a drop of honey has to be placed onto each image. If the honey smells like an advertisement, it is usually disarded.