To avoid confusion. We had three Nakamura's at office one time, so we defaulted to first names. We currently have two Nomura's and we use nicknames for them.
I've also met people who – against the normal, mainstream Japanese way – basically always prefer their first names, because their last name is so common people are going to mix them up with... someone. I sometimes sense a kind of an aura from these people: they don't want to be seen as just "one of the Satо̄s or Tanakas". (Btw. those are the exact names of the people that came to mind, whom I felt that aura of not wanting to use their last name.)
I think that those kind of people would choose the rarer name for their kids. But they don't also want to change theirs, because they are in the middle of a professional carrier, and being the busy people they are, they don't want to stir things up.
I've also met people who – against the normal, mainstream Japanese way – basically always prefer their first names, because their last name is so common people are going to mix them up with... someone. I sometimes sense a kind of an aura from these people: they don't want to be seen as just "one of the Satо̄s or Tanakas". (Btw. those are the exact names of the people that came to mind, whom I felt that aura of not wanting to use their last name.)
I think that those kind of people would choose the rarer name for their kids. But they don't also want to change theirs, because they are in the middle of a professional carrier, and being the busy people they are, they don't want to stir things up.