I think the debate there would generally touch upon what constitutes a braking a mechanism, and not the validity of a braking mechanism. Otherwise we'd see people favoring brakeless SS bikes w/ freewheel cogs and calling *those* folks a bunch of nancified so-and-sos.

As a side note, I'm glad my fixie-ridin' fiancee not only believes in helmets, but also having a traditional hand-operated front brake for panic stops. The real trick is getting her to carry spare tubes, some sort of pump, and doing safety checks semi-regularly...