You should use the individuals personal name for their name within OpenERP because it is better for communication purposes and, like you pointed out, the audit trail.

A good approach for keeping track of job positions is to use the Human Resources module, to create "Employee" records and link them to your users. So, the John Smith user would also have an Employee record that would be linked to his user account.

This means that he can change departments easily while maintaining appropriate details. It is also a little nicer for your users to be referred to as people instead of functions ;)

/Max