Macworld posted an article reporting that 600,000 preorders were taken for the iPhone 4 yesterday.
After suspending preorders, Apple issued a statement including an apology:
Yesterday Apple and its carrier partners took pre-orders for more than 600,000 of Apple’s new iPhone 4. It was the largest number of pre-orders Apple has ever taken in a single day and was far higher than we anticipated, resulting in many order and approval system malfunctions. Many customers were turned away or abandoned the process in frustration. We apologize to everyone who encountered difficulties, and hope that they will try again or visit an Apple or carrier store once the iPhone 4 is in stock.
Expect to see iPhone 4 models selling on eBay for triple retail very soon. Some are claiming the demand is 10 times higher than for the 3Gs. This demand is surely what caused the host of issues that precipitated the apology from Apple.