Quote Originally Posted by thir View Post
Is this true? Is, for instance, an online connection infidelity? Are SMS's?
Where is the line drawn?

IMHO, if it is an interaction that you can not let your partner know about, then it is inappropriate, regardless the format (physical, emotional, flirting, instant messaging, texting, twittering, or platonic lunch dates with a coworker) of the interaction. Whether that constitutes as infidelity, only you and your partner can decide that.