I saw it first on the Rachel Zoe Project, I saw it again while reviewing the Milan a/w 2010 shows (which I'll try to put up really soon) but I didn't absolutely fall head over heels for it until I saw it on the shoulders of Sienna Miller at the annual Met Gala.
I love the way its risque in the front but still uber glamourous. The plunging neckline and short hemline could have gone very wrong, but it ended up not looking sluty at all (I mean as long as your completely flat.) Even in these basic photographs you can see the beautiful embroidery and details in the dress making it more haut counture rather than RTW.
Seriously. I know I sound like a ten year old raving about pretty things, but just look at those layers! I want to get married in this dress.