Here is a Resources for attorneys Blog entry on Metadata.  Need to know about it?  They say that not knowing leads to malpractice:

"In today’s computer dependant world, the zealous advocate must be able to navigate his way through every conceivable form of discovery in order to effectively represent his or her client. Failure to seek the appropriate records or the failure to respond to discovery requests with the appropriate electronic discovery knowledge could potentially expose both client and attorney to the risk of sanctions for discovery abuses and/or result in the spoliation of evidence. Knowledge of the electronic evidence is crucial to any attorney hoping to retain clients. Once electronic evidence is in hand though, an attorney faces additional obstacles, specifically, regarding how to properly use such evidence. Gaining a true understanding of metadata can mean the difference between success and failure"