Here’s a good quote from Mark Zuckerberg in his visit to the Seattle Facebook office:
“One thing you find in engineering is a really good person is like 10 times as productive as pretty good person. I’m not talking about a bad person – I think bad people are negatively productive because of all the externalities of stuff that has to be cleaned up around them – but pretty good people, who would be the best engineer at a lot of companies.”
Source: Seattle Times