For me, number four is very important. I see people knowing and greeting so many people and i am wondering how well they know them? Which are their friends and which just acquaintances?
I don't judge them based on that but i am really curious when i see things like that.
Anyway i think internet is a place full of introverts with lot of interesting things to read/create etc and it definitely not the same as anti-social.
you know what? i have always wondered about the same thing too! haha