I think that 'reference-request' could be put into the questions themselves. I think all answers should be backed by references where possible. The use of this tag implies that some questions do not *have* to have references.
The problem with not providing references is that there are various opinions, and interpretations. I think Christianity.SE and Judaism.SE both have a citation-strongly-preferred policy, as does Skeptics.SE. This is because they all have various viewpoints.