If you have a world in 1.7.4 with items in a chest and then open the world in a 1.8 snapshot, then the items will not be there when you go BACK into 1.7.4

I know EXACTLY why this is happening:

When you go into the new shapshot, the datavalues of the items in the chest get changed into the names (for example 1 becomes minecraft:stone)

When you go back into 1.7.4 in the same world, the NBT tag of the chest still contains minecraft:stone instead of 1 and the 1.7.4 world is unable to understand "minecraft:stone" and just deletes the item.

The same thing happens with villager trades if opened on 1.8 then on 1.7 and can be tested by spawning a villager instead of placing a chest.

How to test:
1. Create a new world in 1.7.4
2. Place a chest and put items in the chest
3. Open the same world in the latest 1.8 snapshot
4. Open the chest again (everything should be fine)
5. Open the same world in 1.7.4 yet again
6. Open the chest again (which is now completely empty)

(The same thing happens with villager trades if opened on 1.8 then on 1.7 and can be tested by spawning a villager instead of placing a chest.)

This ruins survival worlds and custom maps (I had to fix half of my map because I opened it in 14w04a)