I started running brakeless one winter when I pulled the lever because a cab was pulling a u-turn right in front of me and I didn't have time for anything else. It stuck closed, and I took the brake off a few days later. It was actually the fact I hadn't used the brake for a couple months that resulted in it failing on me. Even then, it didn't fail, I stopped. It's just that I couldn't go again.

I went back to a brake on that frame later, but then picked up a Bianchi track bike that had nowhere near the room for a brake. I rode it around for awhile brakeless on the streets, but didn't like having to slow down so much to feel like I was in control, especially on any longer downhills...

The Bianchi is getting a new fork this spring so that I can run a brake, and both my other fixies are running front brakes now. One of them is actually going to be running a rear, as well. I plan on putting a rack and fenders on that one, and think that the extra weight justifies the rear. It will be set up as mostly a minimal pressure drag brake, for scrubbing off speed and cadence when I need it.

In the end, I totally recommend that people know what they are doing before just jumping into traffic. That goes for any type of riding. Like it or not, brakeless without skills is more of a risk than a brake and no skills. Brakeless and skills vs brakes and skills is a whole different argument.