Just a reminder....
I was riding last weekend on a group ride and, before I started, one of the guys reminded me that the quick release on my front brake was open. I'd been monkeying with the front wheel previously, so I'd probably just forgotten about it. And, because the QR on road bike brakes leaves it partially-functional, I kinda miss it when I check the brakes because I'm so used to V-brakes where, if the QR's detatched, it's fairly obvious.
I'd noticed that it was a little soft on the way in, so it was already in my mind that I should check it before we started. I closed the quick release and went on the ride. The guy who pointed it out works at a bike shop and reminded me that, while the rear brake was somewhat optional, the front brake was pretty much a strict requirement.
Naturally, mid ride, I was panic-braking to avoid an unexpected car and I felt a "CLINK!" and the rear brake was suddenly useless. Thankfully, my front brake was still working, so I was able to stop just fine. Turns out that the rear nut was loose, but since it was just the rear brake and the front brake was still working, I continued on for a bit so I wouldn't get dropped.
Now, I understand that there's a lot of people who are scared of the front brake, because they usually ask me how I didn't fly over the bars when I tell them the story of riding downhill with only a front brake. I've seen bikes that came with one where people have deliberately disabled it. And it bugs me. Because, unless you are on a velodrome or other sort of closed cycling track, you really can't avoid the need for brakes. And brakes break. The cable snaps or comes loose or you forget to close the QR or something like that.
And I can and have gone down steep grades on my bike without using the rear brake at all. It's a matter of finesse, really. Only a problem if you try to ride down hills on the rear brake and suddenly try to use the front.