In a corporate env, you want to be able to attach/display extra information about a user:
e.g Phone Number, Geographical Location, etc.
At the simplest level, they are what we (and I guess most corp users) would need.
However, to cater for different requirements, maybe you want to be able to add custom properties to a user.
Other Details:
You may want to mark whether these fields are required or optional
These fields must appear on the "Add New User" form.
You need to be able to map these fields to external user management.
How about a custom field which looks at the issue reporter, looks up associated user fields from LDAP, and displays them? By exposing this info as a custom field, you can then list info like 'reporter company', 'reporter location' in the issue navigator, and generate statistics and bar graphs ('issues per reporter company') on the dashboard.