When a chest, furnace, or any TileEntity with a "front" is spawned using /summon /setblock or from a spawner, it will always reface itself away from walls (overwriting the “Data” tag). If there are no walls around it, it will ALWAYS face south.

Good chance this has to do with when chests are generated in dungeons, and conflicts with the newer spawning methods.

Click on gif below to see an example.
Example World Download with many possible occurances of this happening (requested by dinnerbone): http://www.mediafire.com/download/8gz7fb26algcef0/SP_World_Spinning_Tiles.zip

This happens with chests, trapped chests, furnances, dispensers, droppers, and anything else with a front face to it.

Edit: In 1.7.2 this also affects the /setblock and /summon commands too!