At work, I refused to share my contacts with WhatsUp (and Facebook Inc) and the answer has been that I am excluded from certain conversations. In this circumstance I have lost out?
I like your point about transferability and think that maybe as you point out that this maybe what matters most. This then allows for such projects as Manton Reece’s transfer of Instagram to Micro.blog or Jonathan LaCour’s move to transfer Facebook content using Micropub. A part of me wonders if I retired my Known instance to early?