If you share your reference database with other users, the personal reference list is your tool to still have the personalized database that you want. In a way, you can eat your cake and still have it. First of all, you can limit your database search with the -P switch of the getref command to those references that you added to your personal reference list. But that's not all. With refdb, all fields of a RIS dataset which must be the same for all users (like the title or the journal information), are common and accessible to all users. The information which is likely to differ between users (the reprint status, the availability information, and the notes), are stored separately for each user. If you later retrieve datasets, you will see your own notes for the reference, while your colleague will see his notes. All the "hard" bibliographic information will be the same for both of you, though.
So the personal reference list is essentially a tool to have your own personal information for a dataset and to create a personal, selective view of the database.
Now the question is, how does a reference get into your personal reference list? There are three ways to accomplish this:
If you add a new reference to the database with the addref command, the reference will be automatically added to your personal reference list.
Add an existing reference to your personal reference list with the pickref command. This command will not add personal data to the reference, it just serves the purpose to include this reference into your searches if you limit them to your personal reference list.
If you use the updateref command to modify the information in an existing reference, this reference will also appear in your personal reference list. If you use the -P switch with this command, the data of this reference common to all users will remain untouched, but your personal information (reprint status, availability, notes) will be added.
Remember that one user can act on behalf of a different user with the -U switch, that commands like addref support.
Of course there are also ways to get rid of the references that you once found useful. If you share the database with other users, the first choice should always be the pickref -r command. This just removes your personal information and your association with the reference, while it leaves the common information untouched for other users of the database. Only if you know that no one else is interested in a reference, you should think about using the deleteref command.