I have a front brake, and wouldn't be comfortable riding without it. If you have to stop quickly, a rear wheel skid simply can't stop you as fast as a front brake can. (You should, of course, be careful on slick surfaces, where you wouldn't be going as fast, anyway.)

Once, commuting on a bike trail, I was riding around a blind corner too fast, and a student from the track team came around the other side in my lane. I braked as fast as I could while veering left, and he jumped to his right. I grazed him, but one of us would likely have been injured if I didn't have a brake. Now I take the road more often, and if I do come to a blind corner, I yell or ring my bell. Still, while prudence and foresight can avoid some dangerous situations, to count on prudence and foresight to be able to avoid all of them would be neither prudent nor foresightful.