deadsea - 6:17 pm on Mar 11, 2013 (gmt 0)
My understanding of this was that it is actually implemented by browsers. Browsers don't send full referrer info when clicking from a http to an https site. Browsers only send the domain and protocol, but not the path and query string in the referrer.
I believe you can get full referrer info from Google by fully hosting your site on https.