On a side note, there was a lengthy article in Wired a year ago or so that examined the two methods for producing syntetic diamonds. Here is the archived story:
http://www.wired.com/wired/archive/11.09/diamond.htm
My wife has always said, she doesn't care if the diamond is real or not... just that it is pretty.
As for real diamonds, there is all the issues surrounding where they come from... many come from places that sell the diamonds to support war. If you can, ask for Canadian diamonds. They are just as nice and their proceeds don't go towards spilling more blood...