Outside of Silicon Valley good looking people tend to make more money and are seen as more competent. Within Silicon Valley (and this might only apply to technical roles) the opposite is true. Perception of an engineer's technical prowess is inversely related to how good they look. This phenomenon affects women multiplicatively.
Could be the cause of Software engineer uniform (http://svdictionary.com/words/software-engineer-uniform)
Kilim: Damn a pretty girl just joined our team. We will have to carry her load.
Matthew: Wow. I guess the beauty disadvantage phenomenon is real.