Marx & Engels The Ruling Class and Ruling Ideas
Society is ruled by the class which owns the means of material production in society. The class that has the means of material production also controls the means of mental production so it is also society's main intellectual force. Consequently the ruling ideals are the ideal expression of the dominant material relations. In other words the predominant ideas in a society reflect those of the ruling classes and it's interests. These interests are presented as the common and universal interests of all members of society in order to legitimize the hegemony of the ruling class.
This is done by giving these ideas an "independent existence" from the ruling class in the form of (canonical) history. This is done in three ways. First by separating the governing ideas from the material conditions they where produced in. Second by proving a mystical connection among the successive ideas and regarding them as "self-determined". Third by then removing the mystical connection and personifying the ideas in a series of persons, the thinkers and philosophers.
Gramsci on Hegemony
Gramsci expands Marx & Engels argument by positing that making histories is also a privilege of the ruling class.
The history of the ruling classes according to Gramsci is realized in the state and so the history of the ruling classes is the history of the state. Because the subaltern classes are not unified in a state they lack their own history, consequently their history is intertwined with the history of the ruling classes. That means that ideas of the ruling class are embedded within the ideas of the subaltern. Gramsci posits the subaltern takes ideas from ruling class in the form of common sense, which is heavily influenced by dominant ideology. This creates a 'false consciousness', the believe that the values of the 'common sense' are universal rather than function to support or justify the status-quo.
So the ruling class manifests itself both through domination (by force) of antagonistic groups but more importantly through showing 'intellectual and moral leadership'. The ruling class governs by making alliances and compromises to stay in power for it can not using only dominance.
Cultural hegemony in this sense is a 'soft power' used by the ruling classes.
Speculations about Cultural Hegemony in contemporary society
Ever since the internet has become available to the masses it has undoubtedly empowered people world wide. The distributed nature and ubiquity of the network allow individuals potentially unlimited access to information. Further more it allows for publishing texts or media directly to any user of the network world wide, circumventing the traditional hierarchies of publishing and it allows for easy global communication and commerce.
The big companies that emerged out of the internet have done so because they offered services and infrastructure that made it easier for people to empower themselves in this way. Therefore these companies naturally promote the values and beliefs that have lead to this empowerment. Think of the promotion of things like sharing, commenting, transparency, accessibility and interconnectedness to name a few.
We can think of cultural hegemony as being the beliefs, explanations and values that justify and normalize certain power relations in society. If we do so and look at the values promoted by some of the biggest internet companies certain questions arise.
The internet promised to change the traditional balance of powers, which indeed it did in a way but who benefited the most of this? Google who makes billions, or me who can upload his video to Youtube? Following the theory of culturally hegemony: The ability to share information seems universally empowering but we should ask who it has empowered more, the individual or the corporation?