I think the website knows how many people are watching each couple and for how long they stay online watching them. I also think the couples get paid extra based on how many people view them, That would be a logical explanation as to why some couples perform more in front of the free cameras than the other cameras, or why they tease the cameras that they are going to have sex and end up not doing anything, Leora and Carla both love being in front of the camera and make more money.