iPad sales through the roof? Shortages ahead?

A number of reports are coming in today with extremely high iPad sales numbers and potential shortages.  

First, Fortune follows the Apple Sanity Board (oxymoron?)who have been tallying order numbers from iPads purchased today.  They’ve figured that between the start of sales at 8:30am ET until 10:30am ET, 51,000 orders were taken.  While “50,000 iPads sold in two hours” makes a good headline, there were probably a few iPods and Macs sold during that time period as well.  Apple receives 15,000 orders on a normal day.  

Silicon Alley Insider thinks 20,000/hour are selling, which from the above, seem pretty reasonable.

MacDailyNews reports that people who change their order for in-store pickup won’t receive their iPads on April 3.

Multiple iPad buyers have been told that in order to do such a change, the delivery order would have to be cancelled and a new in-store pickup order completed, but that iPad orders (which began this morning at 8:30am EST) have been “so overwhelming” that new iPad orders may not be available for in-store pickup on April 3.

Earlier estimates were that Apple wanted to make 700,000 iPads in March and a million in April.