What Constitutes an Affair?

I have a question for you. If you are in a committed dating or marriage relationship, what constitutes cheating?

I just read an article about folks who are jumping into the virtual world of Second Life and basically living a "second life" on line. They have an on-line identity (an avatar) that they can manipulate to look however they want. They can marry someone, have children, have any kind of job they want, etc.

Many of the folks on-line are married in real life, but having "pretend" sex online with an avatar.

So, is this cheating??????