Weird, and a little bit scary, IMHO… I’ve just been asked by Brazilian collegues to provide my passport number as I’ve been contributing as one author of a to-be-published conference proceedings edition.
It’s required by editors apparently to avoid identifying homonyms the wrong way…
First time I’ve been confronted to that, and definitely less common than giving the passport number when checking-in at hotels.
I just hope they have proper privacy policy 
