Was doing some work for the PFIC 2009 Conference, and I was looking at the SMS.db of a logical backup.  I was looking at the database in a Hex Editor, and to my surprise I saw a SMS that I received from my former Boss that I had deleted.  So I looked even further and found some more, not just the content of the text, the phone number associated, all what you normally find in a non-deleted text.   So, now one more item that can be retrieved from the logical data, and no need to conduct a intrusive search on the iPhone.  There is a utility for windows that claims to retrieve deleted SMS from the logical backup.  Haven't validated this tool yet.  When I have completed testing, I will post the results.