Get a back brake and just don't use it when you don't want it, but it'll come in handy. When you're riding to the jumps or to school or through the town, brakeless is awful, and it just wears out your shoes and such. Brakeless saves weight, but not too much. You can do better things to save weight.
this question is like, MTB or BMX, Black or White, Fork or No fork, its all your prefference. If you wanna try ridding a bmx without brakes go for it. If you dont like it, isntall the breaks.
Damnit, you are not getting it are you? This is the pinkbike verison of Deal or No Deal, "Brake or no Brake" Not "Who wants to be a epic MTBikeionere?" Ghawd. I am insulted. lol
Back on topic. If you ride dirt, use brakes. What happens if your riding in the woods, and a whale pops out in front of you? Think about it for a minute...