As a consultant, I've joined a lot of projects, usually not right when the team is forming. Over the years, I've developed a few heuristics that tell me a lot about the psychological health of the team. Who lunches together? When someone says "whole team meeting," who is invited? Listen for the "us and them" language. How inclusive is the "us" and who is relegated to "them?" These simple observations speak volumes about the perception of the development team. You can see who they consider their stakeholders, their allies, and their opponents.
Ten years ago, for example, the users were always "them." Testing and QA was always "them." Today, particularly on agile teams, testers and users often get "us" status (As an aside, this may be why startups show such great productivity in the early days. The company isn't big enough to allow "us" and "them" thinking to set in. Of course, the converse is true as well: us and them thinking in a startup might be a failure indicator to watch out for!). Watch out if an "us" suddenly becomes "them." Trouble is brewing!
Any conversation can create a "happy accident;" some understanding that obviates a requirement, avoids a potential bug, reduces cost, or improves the outcome in some other way. Conversations prevented thanks to an armed-camp mentality are opportunities lost.
One of the most persistent and perplexing "us" and "them" divisions I see is between development and operations. Maybe it's due to the high org-chart distance (OCD) between development groups and operations groups. Maybe it's because development doesn't tend to plan as far ahead as operations does. Maybe it's just due to a long-term dynamic of requests and refusals that sets each new conversation up for conflict. Whatever the cause, two groups that should absolutely be working as partners often end up in conflict, or worse, barely speaking at all.
This has serious consequences. People in the "us" tent get their requests built very quickly and accurately. People in the "them" tent get told to write specifications. Specifications have their place. Specifications are great for the fourth or fifth iteration of a well-defined process. During development, though, ideas need to be explored, not specified. If a developer has a vague idea about using the storage area network to rapidly move large volumes of data from the content management system into production, but he doesn't know how to write the request, the idea will wither on the vine.
The development-operations divide virtually ensures that applications will not be transitioned to operations as effectively as possible. Some vital bits of knowledge just don't fit into a document template. For example, developers have knowledge about the internals of the application that can help diagnose and recover from system failures. (Developer: "Oh, when you see all the request handling threads blocked inside the K2 client library, just bounce the search servers. The app will come right back." Operations: "Roger that. What's a thread?") These gaps in knowledge degrade uptime, either by extending outages or preventing operations from intervening. If the company culture is at all political, one or two incidents of downtime will be enough to start the finger-pointing between development and operations. Once that corrosive dynamic gets started, nothing short of changing the personnel or the leadership will stop it.