Amazon.com’s Kindle DX is now sold out “due to heavy customer demand” and is taking four to six weeks to ship, according to a message on the Amazon (NSDQ: AMZN) website that apparently went up this weekend. If that sounds familiar, it’s because the device’s two predecessors—the Kindle and the Kindle 2—were also plagued with shortages.

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In the DX’s case, however, Amazon seems to have managed demand somewhat better. At one point, the Kindle 2 had a an 11-13 week wait and the original Kindle was also out of stock for months. Of course, it’s impossible to gauge just how successful sales have really been since Amazon won’t release data—and possibly never will (CEO Jeff Bezos said in late May that “there is a competitive advantage to keeping the numbers close.”) In the meantime, as TechFlash points out, the quick sellouts, coupled with the refusal to release sales numbers, provide fodder to cynics who say that Amazon is cleverly controlling stock to build buzz.