The earlier posts hit the nail right on the head. Allow me to paraphrase a little: if you have questions as to whether something you are about to do is cheating, don't do it; As has been pointed out, relationships transcend just the physical. It also encompasses the mental. It is possible to have emotional bonds with a person you have not physically met, and it follows that you can then invalidate one's sense of self-fidelity.
Another point that was alluded to: if it is something that you need to hide from your significant other for fears of discovery, then it is possibly can be construed as cheating. Thus, I no longer send cyber-kisses, and am stingy with my e-hugs. I don't wanna get sliced up!!!!
