I thought this is interesting-- because of all the conspiracy theories I've heard on this site as to why the green receipts get lost... My friend works one of the big machines that process several hundred thousand letters in a shift. I was asking him why the return receipt often get lost. His answer was pretty simple. When the letters are being sent out the machine operators are supposed to pull them out and give it over to the manual sorter side. This is because they are often stiffer than normal letters and cause problems or get lost in the machine. They are the only kind of letter that have to be removed and most operators are lazy and just don't care. Then on the otherside when the green cards are coming back they often fall through the machines because they are so small(remember they are smaller than both a post card and an envelope). Viola, no conspiracy, just a poorly run government agency(but aren't they all?). This is probably a good reason to use the online certified mail at usps.com
