Update: Reader Tim Y. found the iPad refurbs hiding out on Apple's online store. While they are accessible via searching the store, there's no navigation slot for them (or for the iPhone 4, for that matter) under Apple's clearance section.
So it's almost six months after the iPad's US release -- and there are still no iPad refurbs in the Apple Store. At a time when AT&T is already selling refurb iPhone 4's, which just debuted this Summer, iPad refurbs are noticeably absent from normal retail channels.
The iPad, in fact, remains in a launch phase. It will only start hitting major US retailers like Target in October and is continuing to roll out overseas. The iPad launches tomorrow in China, with prices starting at CNY 3988.
Although Apple is certain to be already working on the next generation of iPad, it's clear that its high demand continues to produce limited availability. We may not be seeing refurbished units for some time yet.