Lately, I've started seeing this a lot in my Minecraft server log:
Attempted to place a tile entity where there was no entity tile!
Sometimes I see it a lot, sometimes not at all.
What does it mean?
Internally, the game refers to blocks as "tiles" and non-blocks (mobs, dropped items, minecarts, etc.) as "entities". Some blocks need extra information associated with them (chests have inventories, furnaces have cook times, …) which are stored as invisible entities called "tile entities". The blocks which have entities associated with them are then "entity tiles". (These are all debug terms; the average player shouldn't ever have to worry about them.)
An error message occurs when, during a chunk load, a tile entity is found, but it's matching entity file isn't. In this case, the entity was one which can contain items (such as a chest, furnace, or dispenser). This can happen because:
The game is good about recovering from such things — the orphaned tile entity is simply discarded and the chunk continues loading — but it does mean something has gone wrong.