There are two poles of fashion that operate along a class-based axis. There are other poles determined by various other differentiations, but they are all rather similar. I am using class in the post-Marxist sense of referring to relations of exchange (and not the Marxist sense of a relation to the means of production).
The classic conception of fashion is of a trickle-down process, ala Simmel. The lower classes seek to emulate the those above them. As John Storey puts it, the superordinate group is then forced to seek new fashion in order to maintain its social difference. Thus producing a fashion cycle, etc.
Fortunati (in “Mobile Phones and Fashion in Post-Modernity”) offers a slightly more complex model whereby fashion ceases to be an elite activity and is more about the socio-cultural massification of something as it becomes popular amongst the middle-class. Fashion emerges from ‘early adopters’ or the ‘street’ and becomes ‘fashionable’ precisely at the point that it is popular. The cyclical character is not effected by the pursuit of distinction-type activity, but the exhaustion of interest. Fashion inevitably tends towards boring. This is an immanent fashion.