Ads targeted specifically towards children do fost a "must have" mentality. These advertisements are targeted towards children because they are aware of the power of the child in the household. Parents are more likely to satisfy their child, and ignore economical aspects of decision-making. This basically starts the support for "consumerism is happiness" at a very young age.
Children are too young to understand that advertisers are trying to get them to buy something. When they see advertisements they assume that this is something they should have and do not understand the value attached to it. It breeds consumerism and takes advantage of a child's misunderstanding. Advertisers should be required to have some kind of disclaimer or only advertise to adults and older children.