I just joined a group, and got a rare ring and Legendary off of the first pack of mobs we killed. (No Nephalem Valor). As soon as I told the group, the Barbarian said it was because he had 200 Magic Find and demanded that I give him the Legendary staff because it only dropped because of him.
I immediately hit "leave game" and placed him on block when he began messaging me. I am curious now, since I didn't have any Neph. Valor if he was right about his Magic Find increasing my loot drops? If so, I'm going to get a group together of players wearing nothing but "MF" gear!!