I feel that as professionals, we should have our first and last name on our ID badge.  As I learned in nursing school, only waitress and strippers go by only their first names!  However, there are several situations in which a care provider would want to limit personal information available to patients - in prisons, in psych wards, in the ED - where patients may use names to locate staff to harass or harm.   So care facilities should determine where these high risk areas may be and allow staff in these areas to limit ID tags to first name only, or even pseudonym.