Think "adultery/cheating" is a very broad term that each difines differently on many levels.
If my finding sexual stimulation through an on-line D/s relationship is considered cheating/adultery then the same would need to be applied to my husbands desire to look at porn on-line. After all... same ending results for each person just a different method in getting there...
Secondly, not to sound like Clinton, but what does the foundation of "cheating/adultery" really mean. Is it just the sexual stimulation or is it actual physical intercourse or is it simply having the emotional needs met by another?
And... does the other spouse not know because they don't want to know?
And from one's perspective, up bringing, culture, etc. it may be defined as cheating/adultery. That may not be the same case for others though based on the same criteria.
And, before fingers get pointed at the "adulterous/cheating" spouse.... why has the "cheating" occurred? Where there other options? What were those negatives?
Each situation is extremely different based on the people involved and the circumstances... so i don't think there is one truly clear cut answer. It is something that each person has to look at, evaluate, and decide for themselves... and it isn't up to the rest of the world to judge the decision that comes from it.