Right now, it seems you must have someone explicitly share a Xap or Component to edit it. Unfortunately, editing is also the only way to view the scripts, data flow, etc. A key use case is to use others' components to do things like troubleshoot issues, use it as a beginning point for new Xaps, customize it locally to suit your needs, etc.
Obviously you should not be able to push changes back to the staging area without proper permissions, but you should at least be able to see and edit details in your local sandbox, even if you don't personally know the original developer.
There might be reasons, e.g. intellectual property, that you wouldn't want people to look at details of others' code, but that should be an option when sending something to staging.