> I find this rather ridiculous. Most people I know have multiple groups of friends, little cross-over between them, and are happy to share different things about themselves with different groups.

That's not that ridiculous. Anecdotical evidence no. 2, neither I nor anyone I know uses groups or lists on FB. And regarding the gulf experience, yesterday I just posted a soccer-related status on my FB wall and I received likes from 2 ladies, one of whom I haven't seen in 15 years and the other just recovering from cancer, either way, I wouldn't have put them in any "interested-in-soccer" list.