>>1199130really slim bars are something you see more and more of in racing, Hansen has been on the slimmest allowed for a while. I have 36cm on my road bike which are really narrow. After 1 or 2 rides they feel completely natural, I don't see any issue with them being unsafe. When I use normal 42cm bars on a road bike now it feels like I'm steering a bus.
How much faster they make you from the aero benefit is extremely noticeable.