though im not from sf, ive been there a quite few times, though ive never ridden brakeless there, it seems very doable. ive ridden some big hills up and down, brakeless (check out the wall in philly and most pittshburgh hills, which get no respect) and ive managed ok. also, you gotta figure, these guys are bombing these hills cause they are on camera and have to do cool ****. not to detract from anything, but you gotta believe that they ride somewhat safer when not trying to impress mass amounts of hipsters. i value safety, but i guess thats why im not a "pro" fixie rider