My single speed road bike has just been sitting around since I switched to a commuter multispeed bike to get to work/elsewhere. I've been thinking about converting my single speed to a fixed gear for tooling around; that vid may be the tipping point for me.
Fixies have a nasty habit of throwing people over the bars, if ones suddenly tries to "coast".
I've watched the Critical Mass rides here in SD, and from the starting point they immediately head down a huge steep hill into downtown. The fixies have a lot of trouble on this hill and I've seen them throw people pretty spectacularly as they gather speed and their legs can't keep up. Which always made me think "Why not just have a handbrake too, in case of emergencies/steep hills?"