There are no iPads in any of the four Apple stores I called in the Boston area for three days now. If any units arrive they sell out in minutes. This is still with a limit of 2 per person and no 3G units available. Also, bulk purchases by education are being delayed.
Now I have no data for the rest of the country, but there have been notes from analysts saying that stock-outs are occurring sporadically. My experience tells me that it’s a pretty serious retail shortage. On the other hand, the on-line store is still delivering with one week shipment times.
It could be that the international trade or “mules” are taking large shipments overseas. To discourage this, perhaps Apple is giving preference to mail order over in-store purchase. The phenomenon is similar to what was observed with the first version of iPhone. Apple was limiting sales to 5 per person and eventually banned cash purchases.
[UPDATE] Still sold out 6 days later.