The fashion of favoring all things anti-establishment regardless of their individual merits: alter-native medicine, alter-native media, alter-native reality.
The portion of the population that supports ideas and beliefs specifically because they are alternative, rather than mainstream, without regard to the instrinsic meaning of the belief. Ideas that were once alternative, but become mainstream are typically abandoned in favor of new alter-beliefs.
Bob's a a slave to alterculture fashion. He used to be a member of the Global Nuclear Disarmament Club. But when the Cold War ended he joined the Fairtrade Nukes for the Third World Society.