I bought my iPhone 4 about 2 months after it was released (I foolishly waited for the White iPhone) and even then after deciding that I wanted it I still had to wait about two weeks because the demand was still very high and the supply was low. New stock would arrive without notice throughout the day every couple of days, and about an hour or 2 after they would already be sold out.
One Saturday morning I called and was told that they had just received a new shipment like 15 minutes before, so I rushed down and I had to wait in a small line for about 45 minutes.