One of the problems is that the girls (and sometimes the guys) are pestered at the hotels by passengers who have seen their names on their badges. For this reason, BA allow cabin crew to use only their christian name on their badges. If this is their choice, then it would be rather ungracious of us to blurt out their full name on the PA. We take the safety of our cabin crew colleagues very seriously, and would not put them at risk by giving unnecessary information.
Airclues