My right shifter cable broke at about 3500 miles (Shimano 105 - 10-speed). A few hundred miles later the crosspiece the the brake cable threads through broke on the same side. The shift cable I understand since it gets used plenty. The brake thing not so much. My only thought is that it's a silly little piece of plastic and it just wore out.

I will now make it a point to replace cables each winter. Breaking a cable ruined the chance for a good day of riding.