A few days ago in a match I was playing support. I was moving through the river while our mid laner went into the enemy jungle chasing a low hp opponent. Without much thought I followed my teammate. Both of us were ambushed by the enemy team, and killed. We could have avoided this mistake if either of us paid better attention to the situation (or map awareness). Instead it seemed that both of us got tunnel vision. The mid laner apologized by saying how his or her carelessness got both of us killed. I said it was no big deal we just need to pay more attention in later game.
Scenarios like this happen very often in League of Legends where collective decisions are made with people trusting each other's (poor) judgment, especially when players are tired or tilted. In less ideal scenarios players could become quite toxic and begin to blame each other for their mistakes, even when in actuality none of them has taken the most rational action towards maximizing the team's chance to win.
When strangers are put in a team to work together intensively for more than thirty minutes, what I have often observed is that players temporarily put considerable trust in teammates' judgment. This way cognitive activities such as decision-making become distributed across several teammates. The could be the only way a team of strangers responds to urgent situations, since not everyone could make best decisions in a few seconds, and it is so much easier to just follow others. But this also means the possibility that there are free riders who just don't expend cognitive effort in teamwork. This is a very bad scenario especially when the players are expected to fulfill certain roles. For example, jungler is an important leadership role and a jungler who doesn't appear to be thinking much about objectives and map control is highly likely to ruin the match for the team. I wonder if there are design mechanisms to keep junglers alert. (The monster timers definitely help a lot.)
BTW, I really am thankful that an anonymous friend gifted me 5000RP in game :)