That may depend on your setup. I have RPM arms/carriers on the front and true-track on the rear. I have yet to have the ball pop out on me.
A few years back on my first revo, they would pop out on me once in a great while on a hard off kilter landing that caused the rim to dig into the ground. I'm pretty sure I would have snapped a stock carrier, but as it was, it just popped out through the back. 5 minutes wrenching and I was back up and running.
I had my older rig sitting higher than my current one. Was probably the reason it popped them out more frequently. The extra angle at full extension was enough to make it easier for them to pull through.