In his book the Wisdom of the Crowds, James Surowiecki mentions that in the early part of the 20th century, the American naturalist William Beebe King came  upon a strange site in the Guiana jungle.  A group of army ants was moving in a huge circle.  The circle was 1200 feet in circumference and took each ant 2  1/2 hours to complete the loop.  The ants continued to circle for two days.
Most of them died.

This phenomenon, a "circular mill," is created when army ants find themselves separated from their colony.  Once they're lost they obey a simple rule: follow  the ant in front of you.  

Eventually, a few ants straddle off from the "mill" and those directly behind them will follow them away.
Every move an ant makes depends on what its fellow ants do. Since ants will not act independently, it's likely that most, if not all, will not break their march to  death.

We are independent decision makers as well as followers. While we are subject to the influence of others, we will not march in a death circle just because  others are doing so.
However, the more personal contact and influence exerted on each of us within a group makes it less likely that the groups decisions will be wise ones.

Why would that be the case?
 
If we influence each other on a regular basis, trusting each others beliefs in a variety of topics, we  will eventually make mistakes.  The closer we become, the  greater the likelihood of making not just small mistakes but larger ones as well.
Certainly we would continue to get smarter as individuals, but we could get collectively dumber as a group. It's hard to remain the singular voice of reason  when the rest of our associates disagree with us.

Surowiecki's book mentions a group of social psychologist who, in 1968, put a single person on the street corner and had him look up at the empty sky for 60  seconds. His looking up in the sky caused a small number of those waking by to look up as well.
Next, the psychologists had 5 men look up. The result was that four times as many people looked up.
As more men were seen looking up, a greater number of passerbys stopped to see what all the fuss was about. When the number exceeded 15 men looking  up, more than 80% of the passerby's also looked up.

Certainly it's possible to suggest many reasons why the passerby's felt the need to look up.
A simple reason could be that if a large number of people were  looking up, then there must be something to see.
If one were not sure of the reason the group was looking up, then why not follow along?  

Keep in mind that Surowiecki's book is about the wisdom of crowds. He maintains that the group usually knows best, so following the group usually makes  sense.

However, Surowiecki suggests that if too many people adapt the strategy of following the crowd, they stop being sensible and the group stops being smart.

In essence, they become army ants.  

The reality of this can be seen in the dogmatic use of training methods from an earlier era despite a large body of information that denies either the need or the viability of the methods. Each ant is following the one in front of them because they believe that the one in front of them knows something that they don't.

A circle has no front.