Players have been asking for a way to track even their gray quests for a long time (in order to go back and do them for lore or reputation value), and now it looks like Blizzard is finally listening. Tigole says that in the next Wrath beta build, even gray quests will be trackable on the minimap, like normal quests are now. While a few players argued when the minimap first got updated that it would make the game way too easy, I've found (as I've been leveling my alt again lately) that it actually lets you focus on the important part of the game -- the quest text. Not poking around looking for those exclamation points keeps your mind on what's actually going on as you go back to a quest giver, and makes it more fun as you turn in the overdeveloped gizzard or whatever you're giving away.
So good news on this one for completists -- if you've been thinking about going back and hunting down all of the old quests, for reputation, for the new achievements, or just for the heck of it, you might as well wait until you can see them on the minimap.