i've ridden a segway and i much prefer a fixed gear bicycle. if you read the whole thread you see that "no brakes" is inaccurate; segways employ dynamic braking of a fashion analogous to slowing a fixed gear by applying backpressure. in principle, dynamic braking employs the same engine to slow the machine as it does to speed it, so one is tempted to think that our legs have enough power to slow a fixed gear sufficiently. this is probably true most of the time, for many riders. sometimes you may have to provide more stopping power than you have ever supplied for speeding up, however, and in these situations a mechanical brake could be used to advantage. if you are familiar with how it works, that is; the "i only use it in emergencies" approach may be more dangerous than having no mechanical brake at all.