There are two variants to the 'moveChunk' command, one using 'find' and the other using 'bounds'. On http://docs.mongodb.org/manual/reference/command/moveChunk/ we state that the bounds variant should be used for hashed shard keys. We don't say anything similar for the find variant. We should either:

• state that this form should not be used for hashed shard keys (balancing the statement in the bounds variant), or (optionally / additionally)
• state that the document supplied to the find in the case of a hashed shard key should use the hashed value of the shard key, not the raw value of the shard key (problem is that to get the hash you need to use the internal _hasBSONElement command)