I seem to remember being able to select different bones of a rig while in weight paint mode.
However, now when I try to do this I end up selecting a face (used for masking) instead of the bone:
How did I change this and how can I select bones while in weight paint mode?
Upon further investigation this face selection is used for masking, and bones can be selected with ⎈ Ctrl RMB.
However, I can't figure out where this behavior came from.. I've tested it in blender 2.69 through 2.73, and in every version blender defaults to selecting bones with plain RMB and there seems to be no way to select or enable selection of faces while in weight paint mode. I couldn't find any settings regarding masking while in weight paint either.
So the real question is: What did I enable to allow this face selection masking feature?