Group Formation
People have tendencies far beyond their imagination.
We tend to group, to band.
We tend to do so many things, that some go unnoticed.
Have you ever paid attention to how you position yourself while in a moving group?
Each person, according to his own personality, tends to assume certain positions within a group while moving, lets say, on the street going to lunch.
So I can exemplify my point I shall illustrate with these pictures, in the assumption of a 5 people group.
I for one, have either one of two preferences to position myself, either as a leader, taking point, or in any leftward position of guard. In my case, leadership is natural, but only within my group and when I'm leading. Left wing is because my left side is my defensive side, stronger to absorb blows, but less precise.
Even though I associate positioning with aircraft formation, anything workd

First off, the arrow formation.
There are basically 3 places to position in this case. The other two are symmetric. You can either be the leader, taking up front, the inside protection, or the outside wing.Pentagon Formation.
This is very common within five people group, as it maintains the generally equal distance among opposites. Assuming basic orientation, it goes much like the arrow, with the difference that there is no outside wings, and no we have back positions. If oriented downward (that is, with two people in front of the group) we get left and right leaders, left and right wings, and back row shield.

Bat Formation. (in the lack of a better name)
Mostly this is an intermediate formation between reverse-pentagon and arrow. The roles are much like pentagon formation, except that the back row shield now is a center back shield. Arrow Tip Formation.
A variation of the arrow formation, with the outside wings assuming left and right back wings. This way they protect each other, and share defense over the sides with the, now, left and right front wings, leaving them more prepared to defend the back. Cross Formation.
This unusual formation is rarely static. It usually is a hybrid of orbital satellites. While in this we have a center person, either a weak one to be protected, or the center in which everything revolves. The other four, may take a plus sign formation, with each one protecting a side, a X formation, which usually functions the same way, but with the responsibility for the main facings divided among the nearest two, or, most commonly, they can keep dynamically revolving over the center.

These are just some examples.
Most people, just fall under a part of the formation as a natural thing, either because they prefer to follow from behind, walk without anyone in front, or talk with someone at their own pace. No one pays much attention, and I stress that making an effort to position yourself in a specific place is a sign of OCD, so watch out. This is something that you should not do on purpose, rather just go with the flow of the group.