ditto to nc_guy's response....
but having said that, sometimes facials are funny because you never really know how a guy is going to shoot until he actually shoots.... in some cases, it's quite an unexpected surprise, and laughing is just one of those automatic reactions that some people have when unexpected things like that suddenly happen.... just look at it this way: if a guy shoots that hard as a result of your skills, you should accept it as a compliment because it means you did a good job.... it's certainly much better than some dude telling you he cums like a champ and then dribbles like a leaky faucet....