They can use this to try to become intimate with other people that think they are not who they really are. They can use this illusion to make someone have net intercourse with them and for some unscrupulous people, can end up publishing the transcript of these conversations to the net and let others know about the activities of someone online. There is a certain understanding on any online chat, that you are not being recorded, unless it is explicitly stated to you. The ability to put trust into others on the net, is one of the things that shows that people have an identity that they put forth and that others believe in this identity. This is not to say that people can not be untrustworthy on the net.
Word of mouth works the same on the net as it does in everyday life.
If someone says that they do not trust or believe in what someone else says, it can lead others to question the identity of some one. The ability to log your own conversations can make it easier to see that someone has contradicted themselves, or see what they have said over a long period of time so that you can find out things that they have not been truthful about. Since in normal conversation it is hard to remember everything that has been said, the power of computer mediated communication allows someone to be able to catch someone in a lie. It is this power that has made a code of ethics that says that if you are logging a conversation, that someone must warn you about it. This makes it so that you can watch what you say when you think you might be overheard.