A turn off would be a guy eating out a girl. I wanna see that pussy get pounded or another girl making a meal out of it. You got a tool, guy. Use it.
Another, more of an annoyance, really, is when the guy is in the way or when the camera guy doesn't know how to hold a fucking camera. What the hell is going through his head? "She's taking it hard in the ass. Let's sit back a ways and get a shot of the guys leg. That's so really hot. Check out that man leg!" or "God, that chick is hot! Oh my God, I so wanna get a shot...of the guy's face! That would be cool. Because that's what every straight guy watching this porno wants. He wants to see this guy's face while he makes out some facial expressions similar to my constipated grandfather while on the crapper. This shit is so hot!"
At least that's what I think could be the case. Not quite sure though.