Quick thought to be expanded later... most "models" of decision-making (at least, the ones that assume some kind of "rationality of the individual") always start with the idea that people make decisions for themselves. But, as marketeers know, the choices many people make are based on what they think others will think of them. In that regard, then, decision-making is certainly a social issue, rather than an individual choice. Hence more institutional/actor-network stule approaches to innovation, sales, decisions, etc.

Maybe see also Breaking Economic Assumptions.