This is something that's been bugging me for a while and I haven't been able to get a straight answer to IRL. When placing cams in a vertical (or near vertical) crack, the biner on the sling is oriented perpendicular to the rock face (either gate out or gate in).
If you're climbing directly above the cam with the gate facing out then you're basically back clipped since in a fall the rope can pass across the gate (depending on which way you come off).
If the gate is facing into the plane of the wall it risks being smacked open by the edge of the crack in a fall.
This problem pretty much disappears when extending the placement, but I know it's a fairly common practice to clip directly to the cam slings. So how do you avoid these issues?
Well, if it's that big of a deal for you I guess you could always clip another biner to the one clipped to the sling. This would change the orientation of the gate by 90 degrees while only adding about 3 inches to your fall. Good luck out there and stay SAFE! (yer still gonna die)