In Europe, for example, there are several cultures that in greeting, whether they're saying hello or goodbye to their co-workers, their friends, or to loved ones in general, or maybe to each other's friends, it is custom to greet with a kiss and to say goodbye with a kiss on the cheek. Some cultures even kiss or peck on the lips. So I think it just depends on the culture.

When it is a simple kiss like I described above, culturally I don't consider that cheating, I just consider that to be a part of the culture itself. Obviously if there is like romantic kissing like what is seen above with the tongue involved, that can in fact be cheating. In fact I would consider that to be cheating personally because that's way too close for comfort and that goes beyond a cultural thing.