For the second time in a month, Amazon.com has sold out its new electronic reader, the Kindle DX. The online retailer's Kindle DX page now gives a 4 to 6 week wait for the device. In mid-June, the DX was briefly out of stock, but Amazon got shipments going again in a few days. This isn't the first time Amazon has experienced Kindle supply issues -- the company memorably sold out the original version of Kindle in late 2008 (just as the holiday shopping season was getting underway) after an endorsement from Oprah Winfrey. Is Amazon overwhelmed by the demand for Kindles, or, as some suspect, is it keeping Kindle supply low to help generate buzz?