I agree. If I am going to put something online, I expect it to be in the public domain.
I do however try to keep all my online identities, although all real, separate. For example, I don't link my reddit account on my facebook. It's like having different groups of friends, you don't want to force them to hang out together, it would be awkward.
I hate that I have to preface a question as being sincere to ensure that it isn't read as an insult, but here we are.
I don't have those friends anymore. I deserve better. If someone can't take the time to reply to a simple email or text unless it's through Facebook, they're not worth having as friends. Yes, you may lose some friends, but the ones you keep you know are going to be there for you.
I would not want to be your friend.
Facebook has an unreal level of penetration into my friends, literally no other app is so widely used. It's not the best at any of the things I use it for, but it is the single most reliable way to schedule events and communicate with people I know for the least amount of effort.
Of course, they also use SMS, WhatsApp, Snapchat, and Kik as well, so I have to have all of those on my phone.