Agreeing means the providing team understanding and meeting the needs of the consuming team. Teams that can work together to accomplish this wouldn't be called

Agreeing means the providing team understanding and meeting the needs of the consuming team. Teams that can work together to accomplish this wouldn't be called "silos." However, when two teams work together to create an API, or a process or some other self-service mechanism, sometimes the API so good that the teams no longer need to talk to each other. The practices and relationships that enabled communication fade away. Walls go up, silos form, but nobody notices anything wrong, because it seems like efficiency is getting better and better. Over time, though, people start to notice that projects that encounter a need to change the API always fail. The API has become legacy, baggage, a problem. There may still be somebody on the providing team who remembers that they used to get together in the same room with developers from the consuming team to come up with solutions together, and they'll naively suggest that as a solution, but there are now too many assumptions baked in at the management level for that to be allowed to happen. A change in the working relationship between teams means the managers will fight over what this means for different managers' prestige. Somebody's cheese is going to get moved. Managers gear up to go to war over things like that, so upper management dictates a solution that minimizes inter-manager violence, a solution that carefully circumscribes the kinds and amounts of contact that members of the two teams are allowed to have. Voila: silos with windows, and engineers sitting in their respective windows forlornly waving at each other like lovers separated by their parents.