Most cultures have a fear of beings who can change their shape. If you have Navajo friends you've learned not to talk about Skin Walkers, shape shifting entities who can assume many forms. Every culture fears beings that are not who they seem.
Trust in identity is so important in the real physical word we seldom think about it. Obviously your family is your family, your friend are your friends. In real life it's hard and expensive to change your appearance, not to mention the other aspects of identity.
On the internet it's not. Anyone clever enough can appear to be anyone. Is that email from your friend stuck at Antwerp airport with no passport really from your friend? It might be. It might not be. Is the bank we page you signed into really the banks web page? It might be.
Right now the internet is the domain of Skin Walkers. It is impossible sustain community or commerce when you can't be sure about identity. That's the chiefest problem with our networking and the one we will have to fix. And we will have to do it while provide assured elective anonymity. Fortunatly we know how.