In the weeks previous to the release of the Burning Crusade some of my friends were considering saving up a number of quests to turn in once the expansion hit to boost their leveling toward 70. At the time it seemed absurd. You may have a bunch of quests to turn in, but they'd be all over the map, that's what questing was like back in the pre-BC day. I just wanted to get in and get through the Dark Portal.
It may be a viable strategy once Wrath of the Lich King comes out. Taking a look at my alts, some of them still have tons of Netherstorm and Shadowmoon Valley quests. Since it takes 779,700 experience points to go from level 69 to 70, I suspect it'll be around 850,000 to get from 7o to 71. This meas a log full of 25 shiny, complete quests at 10,000-15,000 XP a pop will take you nearly half the way to the next level.
It's not something I'd do on my main character, but I would consider it with an alt. What's your take on saving up quests for quick WotLK XP?