What direction must you install "Faced" fiberglass insulation, and for what reasons?

Faced insulation means one side has a paper backing. Consider the different possible application of install when answering.

The paper on fiberglass is a vapor retarder. The paper should always face the heated space of a home. If in a crawlspace, paper should be facing up against floor decking. If on ceilings or walls, paper should be facing back side of drywall.