Apple's retail outlets across the U.S. have already sold out of the 3G models, which went on sale just last week.
Apple Insider first reported the shortages Thursday. And on Friday more than a dozen Apple Stores, including ones in Boston, Chicago, Denver, Los Angeles, Miami, New York, and San Francisco, said they're fresh out of 3G models, according to Business Week. Apple is allowing customers to put their names on a waiting list, however.
It's possible the iPad's popularity surpassed Apple's rosiest sales predictions, hence the temporary shortage. Or, the U.S. shortage may be a result of Apple stockpiling iPads for its international markets, thereby assuring a steadily supply of tablets across the globe. Some analysts believe the shortage may caused by a shortage of touchsceens used on the iPad.
I managed to get my hands on 5 of them in the past couple months...so they "were" available at least.