would you have a wank with your partner watching? scratch yer minge? pick your nose? shave your pubes? etc. etc. No, but I wouldnt keep it secret that I did those things either (apart from the nose picking, I dont actually do that :o )
Its the secrecy that indicates cheating, not the act itself.
Sex, snogging, sexting, webcamming, emotional connections....all are cheating IF the person doing it keeps it a secret because they know that their relationship would be damaged by them doing it.
If however they are in an open relationship or have an "understanding" and it is not kept secret then no it isnt, because both partners have agreed that its ok within their relationship.
Cheating is secrets and lies.