I've read about shuriken and chakram, I know about throwing sticks, throwing axes, and throwing knives, but I have no idea what Mr. Gygax envisioned when he put darts in D&D as a weapon.
According to the all-wise Wikipedia, darts differ from javelins by being fletched, except it doesn't mention any actual dart usage in warfare, just speculation that men probably used darts before javelins.
My best guess is that they were supposed to be like Roman plumbata. But those were heavy, lead-weighted things thrown overhand. They were meant to be used on the field of battle and fall down into massed units of men. I don't think a wizard would be chucking them in a dungeon.
I'm thinking, even though there is 40 years of precedence, I should just replace darts with throwing knives. That might mean an adjustment in weight, damage, and rate of fire, though.