In some cases the non-OEM cables are not up to par qualitywise. Take for example my cell phone. The OEM cable goes across the data connector and sits firmly in place. I got a non-OEM car charging cable for it which holds itself in by a very tiny piece of plastic. Needless to say it didn't last long.
On the other hand we got a usb charging/data cable for my wifes phone and it's been fine. I got a power/data cable for my gps and it's actually better than the OEM one.
So the morale of the story is, look carefully at the cable, if it looks like crap it probably is.