There are several driving factor for selecting to populate components and divide into components. This is a very good thing to componentize.
The component is the artifact of the SCM that is baselined, so you would expect to populate a component with resources that go together and need to be versioned together. Also, components are part of streams. It is possible to have the same components in different streams (at the same level of configuration or not). If you plan to create several development streams, one per team for an area, then you will probably need to share some resources (copybooks defined by an application that are used by another) between these streams. These shared resources would go in a component provided by a team and used by another in their stream.