My two cents worth.

Life and marriage is a very large game with intricate and complex rules. We were swingers for quite a long time, does that make me a cheater, not by my rules, she knew, she participated and enjoyed with me. The same was true for me. Nothing in our rules said that sex under these conditions was cheating but if either of us slipped out with the others knowledge of the other then that would be cheating.

So I say cyber like any other possible form of cheating depends on the couples rules. As a Master with a slave I will take a pet or two for training purposes with my slave's full knowledge and I don't feel that is cheating either. I will share my slave with members of both sex or I may have her entertain in a carnal manner a male friend of mine without my presences and that to will not be cheating because she will be following my rules.