Even on a good day, brad nails can curl on you. Through your fingers, if you aren't careful.
However, if you look closely at the pointy end of a strip of nails, you'll see that they're cut at an angle on only two sides. (The other two sides are the ones adjacent to their neighbors in the strip.) Anyway, the nail is predisposed to curl in the direction of one of the cut sides.
(Phrased another way, if you hold the nailgun vertical, the nails are prone to curling left or right.)
So you can use this to your advantage... if you're nailing into the edge of plywood, have the nailgun perpendicular to the plywood. That way, if you get a curl, it's probably contained within the ply, as opposed to shooting out the side.
You didn't ask, but a tip for those nasty curl outs: bend the end of the nail back and forth. It'll usually break below the surface of the wood, and you can fill. If there's not much nail to grab, use needlenose pliers.