I have a friend who's transitioned to maybe one post a week on FB. Still also goes on there for "Happy Birthday" wishes and to respond to tags and such a bit.

I have a friend who's transitioned to maybe one post a week on FB. Still also goes on there for "Happy Birthday" wishes and to respond to tags and such a bit. She's on Messenger all day, every day. Messenger appears to be increasingly capturing IM for the masses. From the bit I see. Others can probably speak better to the details, but it seems to represent the best mix of identity and reachability for "normal" human interaction, at least here in this part of the U.S. She runs into a friend of a friend. They don't share any contact information. He reaches out to her, afterward, on Messenger. I need to get in touch with one of her friends. The only connection we have is both being her friend on FB. Messenger does the trick. FB seems to have developed and positioned it quite effectively. Despite / in the face of early and continuing privacy concerns.