I was young (10-11 or so IIRC) but doing a emergency stop quickly down a hill, back when bike maintenance was a "huh?" topic for me I'll admit, I had to use my front brakes as my rear brakes were goners, and sure enough I enjoyed a nice little tumble.

Since then, I've always only used my rear breaks, and kept them well maintained. On some bikes (without integrated brake levers & shifters) I tend to remove the entire front brake assembly. And I have never had any problem with "stopping power" of using a rear brake on it's own.

Jim