A quick look into my FlyerTalk- (Netscape) address-book (with more than 250 addresses/handles etc) show more than 35 handles that have the First- or Lastname included.
I am not aware, since the early days of Flyertalk, that anyone of them ever had any problem because of his easy to identify identity - so far. But I know that airline-/hotel-'lurkers' sometime already did a favour or two to members that were easily identified
I know (the most extreme 'thing' was discovered by Merry then) of some (in the early FlyerTalk days) 'cases', where 'misuse' and 'false identities' created (financial and other) damage (and a lot of mistrust) to other members.