Traditionally, dungeons in WoW were in the hidden corners of the world. Players would get several quests leading them further and further until they finally uncovered the entrance. Deadmines is the classic example of this. This method was pretty good, reinforcing the idea of dungeons being in uncovered areas, while providing a storyline leading up to it. A consequence of this design was that players knew how to get to the dungeon.
With the new Dungeon Finder, this is no longer true. Now, if people die and respawn, they may have no idea where the dungeon is located. Then they have to use the Spirit Healer to respawn, and end up stuck in the middle of nowhere. Alliance has this problem very early, as the first dungeon is Ragefire Chasm, in the middle of Orgrimmar. A lot of people who haven't played Horde have no idea where RFC is.
Imagine trying to find Blackrock Depths if you've never been there before.
Not being able to find your way back to the dungeon is very frustrating. In Cataclysm, word is that Blizzard plans to address this problem by making the player "discover" the dungeon before they can access it through the Dungeon Finder. While this is a reasonable plan, it will cut down on the number of people who can enter a given dungeon at any time, making it harder to find groups.
My solution would be to change how death is handled in dungeons. When you die, the Release Spirit button should be disabled until the group is out of combat. Then if you hit Release, you respawn at the start of the instance. This is a simple mechanism that prevents graveyard-zerging, but removes a lot of the frustration from the run back. As well, it would train people to not release immediately, making it much easier to resurrect them after the fight, instead of having to hunt pixels to find their body.