The places that don't have them probably don't have any in stock and not knowing when they would get anymore might have taken the tact that Newegg takes when they run out of stock on big selling items. They remove the product from their list but it's there if you had it in your wishlist and wanted to look at it that way.
I seriously doubt that Asus pulled them for a socket change. If you watch the Making of a Gigabyte MoBo Vid on YouTube it's too complex a project to replace every socket individually. Which is why Asus gave us a look at 3012 even though Bulldozer is months away.