When we talking about "who owns what" most commonly I hear people discuss it in terms like these:
The way people talk about ownership betray some of my most important values. This is how I translate that kind of talk; "We don't want to touch it", "It is their responsibility", "I am not allowed". You may not want to touch it, but if its in the way of doing your job, I want to see you activate, not wait around for someone else. It may in fact be someone else's responsibility—that doesn't help us make progress in the moment. Do you mean someone is actually penalizing you when you tried?
I value people who activate, get involved, make decisions, and finish work. Every one of these questions avoids getting involved, looks to someone else to make a decision, and does nothing to finish. Finishing something is the only way to create value, hit your goals, and start working on the next thing.
I don't think people are thinking about the implications of their idea of ownership. Here is just a small bit of the quagmire this creates:
When we talk about ownership do we really mean "only owners can modify it"? Does everything only have one owner? Doesn't that make collaboration really really difficult? What does it mean to possess code? Its not even a real thing in the world! What do we do with a list of things that are not owned? If you're claiming ownership why is no one else allowed to touch it? Why do you need such tight control? What value does that create for you? What value is that denying for others? If someone else owns something, and you need a change, and you're not allowed to do it, you've now linked your success to their ability to make that change on your timeline. Is that really how you want to work?
If you own something, and its not successful, does that mean you ought to be fired? I have rarely met anyone who would agree with that statement, but also still believe in "ownership". After all, what is ownership without fully responsibility for the outcomes?
I would love to change how we talk about ownership. I think talking about it this way causes too much stress and anxiety for teams. I want the engineering teams I work with to think about ownership in these terms:
Software Engineering is a team activity. No one person can do it all. No one person owns the code. No one person owns the whole outcome of our work. But you absolutely own getting involved, working hard, and the impact you make. No one but you can stop you.