Earlier quoted context omitted.
I think there is space for an alternative - keep in mind that that doesn't mean that they have to be hugely popular. For example, some online communities I am a part of subsist mainly in chat rooms, or forums. Those communities are so tightly knit in many ways. While a lot of us are also friends on FB, our ties in these communities are still very strong.
I'm in some such communities too, but efforts to get anything going on other sites outside fb come to nothing because you just end up with more social media to keep track of for no real benefit - you can't do anything sufficiently interesting that you can't already do on FB, and you've lost all the network effects for content discovery, rapid dissemination of news or sufficiently entertaining content etc. OK you gain…
Not quite sure what's your point here but most subject specific forums on the web have a huge bunch of users with nicknames and not their real names. With the same reasoning you could also say: no need to close the door to WC when you go there to do your needs since people outside know what you're doing there anyway! If you use VPN and a lot less of your personal information will be sold to advertisers.