BSNYC saw a brakeless freewheel bicycle on the Manhattan Bridge. The only way to stop these kind of bikes is by pressing your shoe into the tire, or by crashing into something. Here's a video of DJ Ted Shred in San Francisco showing how it's done.
Here's another brakeless freewheel video, this one from Stockholm, Sweden. This guy's actually pretty smoking with his technique.
All of that skidding just to stop the bike does a number on the bike's rear tire. Freewheeling bikes like those in the video have essentially an infinite number of "skid patches" (or rather, it's a continuous skid patch), but fixed gear bikes have a limited number of skid patches that's determined by your gearing. If you don't want to use one of the many online skid patch calculators, you can now install a skid patch and gear calculator for your iPhone. The sample display here shows the number of patches for ambidextrous skidders - that means you can skid with either your right or left foot forward which doubles the number of skid patches. I can only skid with my right foot forward.
That iPhone app isn't necessarily just for fixed gear riders -- you input your cog, crank and chainring size to get the gear ratios for your bike gears.