"One is faced with a dilemma: If one places total trust in all other users, one is vulnerable to the antisocial behavior of any malicious user consider the case of viruses. But if one tries to be totally reclusive and isolated, one is not only bored, but one's information universe will cease to grow and be enhanced by interaction with others. The result is that most of us operate in a complicated trade-off zone with various arrangements of trust and security mechanisms."