The launch inventory of the iPhone 4 sold out in less than 24 hours. If you pre-order an iPhone 4 now it will ship by July 2nd, which is a week after launch.
Besides the Apple online store server overload there have been apparently many more issues at the AT&T iPhone 4 pre-ordering in stores and online.
How many iPhone 4 phones Apple already sold is hard to say, but it could be already close to 1 million iPhone 4 devices. Remember that Apple sold 1 million iPhone 3GS over the launch weekend in 2009.
Apple definitely wants to break this record. How about this headline. "Apple pre-sold 1 million iPhone 4 on June 15th world-wide".
Update: Apple announces record breaking 600,000 iPhone 4 pre-orders for day 1.