What cases do the 2006 amendments to the federal rules of civil procedure apply to?

want to know how the new rules relating to electronic discovery apply to cases pending on December 1, 2006 when the rules go into effectWhat cases do the 2006 amendments to the federal rules of civil procedure apply to?
My understanding is that they apply only to cases filed after Dec. 1. However, to the extent that you're thinking about, say, destroying electronic evidence,I'm sure a court would cite to the new rules as evidence that you're spoiling evidence and may hold you responsible therefor.