yes, and no.

fast fixie: front brake
commuter fixie: front brake
townie: no brakes. it's running a 40x19 (that's about 57") with 38c tires, fenders, and a pair of rear basket panniers, so i never get going fast enough for it to matter.

having said that, i frequently ride all the way to and from work without using the brakes on the commuter. most often, i end up using it to hold the front wheel steady while i push down on the bars so that i can rotate the rear wheel into a better starting position.

let's face it: it's much cooler if you don't use the brake, even if you allow yourself to have one.