At the Sony store one of the ds4 nubs was cut like this one is. If you dig into it with your nails or use a knife I can see this happening but I really hope this doesn't happen with normal use. I don't think Sony would build a controller this cheap.
I'd love to see a video of some guy rage playing with a knife hahaha!
Controller issues are nothing new. Every single 360 controller I've had wound up with battery issues within a week (until I bought a 3rd party battery pack. To this day I have no idea what I did wrong originally), and I broke a ps3 controller after a few months (Left stick...admittedly, I had tossed that controller a few times from rage quitting). It's scary how fast it happened in this case, but I could break a current gen controller pretty quickly too if I was rough with it.