[nknight]

It happens all the time, and it can be essentially invisible to management at larger companies. People get close. Cliques with their own sub-cultures will develop, HR-unfriendly and perhaps legally-actionable things will go on behind closed doors when everybody in the room is friends with everybody else.

Nobody will really notice or care until someone with a different worldview starts having to work closely with them and stuff starts bleeding through.

When it goes on for too long, people may get angry and resentful when trouble starts, and then you have a much quieter but more insidious mess...

What? No, I've never seen this happening from the inside! Of course not! I'm a perfect angel!