At what point do you feel it is crossing the line from friendly chat to an affair. Consider the following in your answer- Does the spouse know the chat is happening- Does the spouse have access to the account (password) Meeting a person... Intimate conversation. And so on . At what point is it crossing that friendly line??
When you start breaking the trust you guys had at the start of the relationship; necessarily not in terms of lust but more in terms of the chit-chat you used to have.
- The person online knows more about you then your spouse - You have shared your most intimate moments with ur spouse with the person - On smallest problems you fight with your spouse, but find solace in the words of the online person.
Guess by the last point you realize you have broken plenty of the vows made during marriage, and you have already climbed the first step of the ladder of affair :-)
Ohhhh good question... I think that it becomes an affair when feelings or lust are involved. It shows that you are not taking your emotions and needs to your spouse, but to another person. If you are feeling warm in the face and tingly in the hands as you chat online, then I think it is crossing the line.