Most Helpful Girl
Sometimes bra straps peek out and there's nothing you can do to stop them. And strapless bras don't work for everyone (they don't offer enough support for ladies with bigger boobs to wear all day). Many styles of shirts end up revealing bra straps.
I don't really see the big deal about it if they're peeking out.
Most Helpful Guy
Well, it's "Acceptable", but I think it's trashy. Why would people be interested in your bra straps? Try keeping them hidden under the rest of your top or wear a strapless bra if needed.