"I am not interested in dry economic socialism. We are fighting against misery, but we are also fighting against alienation. One of the fundamental objectives of Marxism is to remove interest, the factor of individual interest, and gain, from people’s psychological motivations. Marx was preoccupied both with economic factors and with their repercussions on the spirit. If communism isn’t interested in this too, it may be a method of distributing goods, but it will never be a revolutionary way of life." - Ernesto "Che" Guevara
Since the newer means of production has lead men to the prosperity of the civilization and so called competition men are isolated from the world, from his countrymen, from his society, from his family, classroom and sometimes from himself, whatever he calls his own world. This is probably a very much generalized way to define Estranged condition of self, in other words alienation.
Alienation is the topic that attracts much to the philosophers after Hegel who declares that much reason have been done in his "Philosphy of right". In his doctoral thesis on the critics of Feuerbach Marx tried to define the commodity fetishishm and its relaltionship or consequences to Estranged Labour or alienation of labour.
Later Sartre and some post modernist tried to define and explain the consequences where they are trying to establish that alienation is something that never ends, specially the post modernist philosophers.