Image via Wikipedia
And here is why:
"Groups tend to spend most of their time discussing the information shared by members,
which is therefore redundant, rather than discussing information known
only to one or a minority of members. This is important because those
groups that do share unique information tend to make better decisions. ... Ironically, ... groups that talked more tended to share less unique information."
Read more about the meta-analysis of 72 studies, involving 4,795 groups and over 17,000 individuals
It is very interesting in relation to focus groups and diverse forms of works where any kind of information is shared or decisions should be taken. Such behavior and tendency to focus on the widely shared informaiton can lead to serious bias of conclusions and decisions taken.