Being a slug I've been smoked by every bike rider ever on my commute home on the highway, and I've noticed that when they're 1/2 mile or more ahead of me, the last thing I see isn't their very bright taillight, it's their hi-viz jersey/shirt/panniers. That's why I wear hi-viz shirts and don't bother with a light on sunny days. I tend not to ride at night, but early in the morning I use my blinky light on the theory that the light will get their attention enough to see me. So far, so good.