AT&T's systems should have been able to handle it.
To give a little perspective, the U.S. stock market alone processes billions of transactions every day. On a "busy" day in U.S. airports, millions of people are traveling.
AT&T doesn't have an excuse. They failed.
I hear that the National Security Agency has some pretty nifty computers that can handle a lot of processing. Maybe AT&T should just buy an Echelon system to handle iPhone pre-orders.
Get real.