... and Graylog CTO here. Ask us anything! :)
I have a centralized logging system, but I can't imagine being so confused about it that I need my logs to tell me that two components interact with each other.
What don't I understand?
The moment more than a few people are involved with your systems, it can get so complex that visualizing dependencies can be extremely helpful and bring a lot of insights.
It's a really fascinating data problem, so we've been loving building tools for seeing into it!