All excellent points, Quiggin, although I'd add "not usually acquaintances or intimates" to "not really equals." So much depends on context. There are times when I will think, "Well, that's a little free and easy" and other times when it seems fine. When the topic is the subject's childhood, it would seem odd to me to use a surname:
And of course with married couples who share a surname you don't really have an option, as with "Eleanor and Franklin" and "Scott and Zelda."
Thank you for sharing your own experience, Ms. Protopopescu. I thought you handled the issue well in your book.
Returning to your review, I appreciated among other things your discussion of the influence of Elizabeth Kendall's work on Homans' account of Balanchine's early years.