Here's my
No matter if it's a B/G or G/G set there are some times its important for at least one talent to be looking straight at the camera. For example when a guy is giving it to a girl from the rear its important to get some shots of the girls face with the guy in the background. She should have eye contact with the camera and if she's a good model will convey a sense of sexual ecstasy or agony depending on the clients requirements. In a shoot I would say I do about 10 - 20% of the images with eye contact where it conveys a strong sexual feeling to the viewer and involves them in the act.