Since it does not appear that JIRA is going to support component hierarchies in the near future, we are planning on creating parent/child relationships in Greenhopper. Parent components will be created in JIRA solely for the purpose of implementing structure to the hierarchy - we do not want our clients to be able to select these components for logging issues against.
Please implement view permissions for components (e.g. administrator allows Component A to be visible only to the group "developers" and Component B visible to "all-users")
This may at least keep some JIRA users happy until JIRA adopts the component hierarachy, that so many users are crying out for....