Can a bar of soap in the bed prevent leg cramps?

I've heard for years, especially from Sydney's family, that a bar of soap in the bed prevents nocturnal leg cramps.  Having never suffered that malady, I've never had occasion to try it.  Now Snopes.com labels the folk belief "undetermined," on the assumption that no one has proven or disproven it.

I'm inclined, like Snopes, to attribute any benefit to the ever-reliable placebo effect, but I'd still like to know whether any scientists have tested this belief.