He always intentionally picks the most dangerous route, thus risking his crewmates' lives tenfold. Zoro, Sanji, Franky, and Brook never seem to care, but Nami, Chopper, and Usopp cry their eyes out when Luffy does that. They even beg him to reconsider, but he just laughs and ignores them.-_-
Luffy is awesome and all, but really? Risking your friends' lives like nothing is bogus. He must be over-confident in his ability to protect them.