Under theory of demand, there are several factors affecting demand for a commodity, and one the of such factor is consumer's taste and preferences. These preferences are governed by four effects, which are demonstrative effect, bandwagon effect, snob effect and Veblen effect.
When we talk about basic definitions of snob effect and bandwagon effect, then then following observations can be made about both if them:
1) Snob effect: It refers to decrease in demand for commodity because other people are consuming them. It is desire of people to be separate or dissociate from common herd.
For instance, if Miss. A and Miss. B are arch rivals of each other. If in a party Miss. A wears a dress, and on seeing it Miss B who also have same dress decided to reject its use from future as other people(here Miss. A is able to have it). Hence from following example we can conclude that demand for particular commodity(dress here), is decreased owing to the fact that other people (here Miss A) is able to have it.
Bandwagon effect: It refers to increase in demand for a commodity to emulate consumption of others or to be associated with a particular group of people. For instance in a college, a particular group of boys are having IPhones excluding one. And on seeing it that particular boy decided to purchase it, to he associated and match consumption behavior of his friends. Hence here demand for a commodity(IPhone here) is increased owing to the fact that group with which he want to associate is able to have.
Both snob effect and bandwagon effect are function of consumption of others, but one lead to increase in demand whereas other decreases demand. Bandwagon effect for a particular brand whose influence is spreading over market is good for it, but not good for society. Similarly from society's view snob effect is not good.