After being ‘in stock’ for a few weeks Amazon have put a small shipping delay of 3-5 days on the Kindle 3. Both the 3g + Wifi and Wifi only models are subject to this restriction. The more expensive DX is in stock.
In addition, Amazon are limiting customers to a total of 5 Kindles per account. If you have a genuine need for more than 5, you have to email Amazon at email@example.com.
When the Kindle was first released at the end of August it was on back-order for a few weeks due to strong pent-up demand. On September 15th Amazon showed the Kindle being in stock, presumably having received a new shipment and satisfying all outstanding orders.
E-book sales in July 2010 showed a surge in demand of over 25% compared to previous months, signaling that e-books are becoming main stream. Amazon recently announced that their sales of e-books exceeded the sales of hardcover books. The e-book revolution is here.