These companies created huge empires and integrated information, culture and entertainment, transforming these in a new form of merchandize.
Before, the advertising industry followed a classic process based on three elements: the client, the advertising company and the medium. All of these were unified by conglomerates. Now every advertising company work together with a marketing company, TV channel, among others. This of course creates more benefits and profits to the owner company because they do not need to hire or pay for other services. In other words this is the perfect way of making profit and minimizing expenses. Every company they need in order to achieve an advertisement, for example, is owned by them.
This also minimizes the competition between companies which also reduces the market and does not leave place for diversity.
All of these factors might seem very positive and productive, the truth is that they are; but only for the companies, society does not benefit from this. It is not safe to have everything unified because it will only lead us to the same ideology and it will restrict our freedom of choice. The important thing is not the number of companies that exists, but the diversity of sources and owners.
Omnicom Group is a strategic holding company whose agencies provide services in: advertising, customer relationship management (CRM), strategic media planning and buying, digital and interactive marketing, direct and promotional marketing, public relations and other specialty communications. Omnicom’s agency networks include BBDO, DDB Worldwide, TBWA Worldwide, Diversified Agency Services (DAS) and Omnicom Media Group (OMG). Omnicom's public relations, CRM and specialty communications agency holdings are managed by its DAS network.
Interpublic Publicis is one of the world’s premier advertising and marketing services companies. The agency brands deliver custom marketing solutions to many of the world’s largest advertisers. We cover the range of marketing disciplines and specialties, from public relations and consumer advertising, to mobile and search engine marketing.
WPP is a company that works in marketing strategies, advertising, every form of marketing communication and in monitoring progress. It is based in London, United Kingdom, is the world's largest communications services group in terms of revenue ,and one of the big six advertising holding companies




http://www.omnicomgroup.com/home
http://www.bbdo.com/worldwide
http://www.ddb.com/
http://en.wikipedia.org/wiki/TBWA_Worldwide#Agencies_and_multihub_creative_networks
http://www.interpublic.com/
http://www.wpp.com/wpp/