Men respond to visual stimulation much more than most women. These sexual scenes provide a wealth of new visuals and can do wonders for the male libido. Women, on the other hand usually have to concentrate more to reach orgasm. These situations are usually not conducive to their sexual functioning unless they have a specific partner they are attracted to. And therein lies the problem.
Jealousies arise when attractions or emotional involements come into play.
Open partner swapping then leads to clandestine affairs and the eventual break up of the marriage. Its a risk that is ever present when you bring new people into an intimate sexual setting. Agree to terms and rules. If one of you is uncomfortable with the course of events, agree that BOTH of you will discontinue the activity completely.