Happens all the time. Sharp eyed people take pictures and it ends up on Engadget or something. Sometimes the retailer slips up and has the item available for purchase before the official launch date, sometimes it's pictures of stock before it's on the shelves taken by employees. A recent example is the Palm Pixie showed up in display cases in Walmart before official launch but it was not yet entered in the system and thus could not yet be purchased.

http://www.engadget.com/2009/11/12/p...le-of-walmart/