When the game encounters an unrecognized or "invalid" item ID, it reacts by crashing and often deleting the chunk which contained the item. Invalid item IDs can be created in a number of ways, including breaking lit redstone lamps with a Silk Touch enchantment, or loading a world from a version where these IDs are considered valid.

Steps to Reproduce:
1. Place a redstone lamp, and power it.
2. In survival, break the lamp with a Silk Touch tool.
3. Observe that the game crashes, and when you reload the world, the chunk will be regenerated (all player-made structures removed, and all mined ores respawned).

Alternate Steps to Reproduce:
1. Load up a world in Minecraft 1.6.2.
2. Type "/give @p 75" (you must have Cheats enabled)
3. Observe that you are given an unlit redstone torch. It seems to work perfectly fine as an item when held, placed in a chest, mounted in an item frame, or placed as a block. No crashes occur.
4. Place the torch in a chest, and save/exit the world.
5. Load the world in 13w37a.
6. Observe that the entire chunk containing the chest has been refreshed.