For a long time, advertisers and their agencies have been trying to achieve greater synergies and efficiencies in their marketing by "integrating" tactics across channels. For example, adding URLs to TV ads, QR codes to print ads, unique 800 numbers for radio ads, etc. Integrating is definitely better than not integrating. But the problems of measurement and attribution could not be solved because the metrics were different in each channel and not easily correlated and multiple marketing touchpoints could be the "cause" of a single customer action.
Social media consists of people's conversations online and their social actions (like sharing or "liking"). These conversations may provide an indication of what they like or dislike.
Traditional agencies' old and broken business model.
In the golden age of television, where agencies produced supremely expensive TV ads for clients, the agency could afford to give away the big idea(s) during the pitch because clients are unlikely to take the idea and then produce the TV ads themselves -- they wouldn't know how to nor would they want to do so.
There are several macro trends that are taking hold now that make the shift of advertising dollars to digital channels increasingly swift and irreversible. Advertisers are no longer willing to commit to AOR relationships In the past, it was more efficient for advertisers to make large commitments to their agency vendors in order to ensure adequate staffing levels for the anticipated work. Now, advertisers are moving towards a project-oriented approach where each project can be “bid out” to multiple vendors to ensure the best team and the best price.