Does it happen: yes, but not when a couple is in a good committed relationship and has great communication. It usually happens when a couple is already in trouble and they are trying to swing to 'save' or 'spice up' a failing relationship. In this case, they are usually already looking for their next partner and once the NRE kicks in, they are out. Swinging magnifies a relationship. If the relationship is strong, it just makes it better. If it is weak, it usually just makes the weakness and flaws more apparent. Stable, loving, communicating, trusting swingers rarely have this happen (from our experience).