According to Engadget, Apple and AT&T are seemingly sending out cancellation emails to some who have pre-ordered the iPhone 4:
We were unable to complete the authorization process for your iPhone order. As a result, we had to cancel your iPhone order. To complete the purchase of your iPhone, please visit an Apple Retail Store or an AT&T company-owned retail store.
We apologize for this inconvenience.
Apple Online Store Team
The word authorization hints at the core of the problem being AT&T. The iPhone 4 pre-ordering process on Apple’s site connected to your AT&T account to continue. Here’s an email from AT&T a few sent to Gizmodo:
Your iPhone order has been cancelled.
Your credit card has not been charged.
If you believe you have received this email in error, please return to the AT&T store where you placed your order.
Some contacted AT&T who responded that Apple had canceled the pre-order due to lack of supply. Apple is responding that AT&T had canceled because of ineligibility. I would recommend calling both Apple and AT&T to confirm your pre-order is intact. Some pre-orders are being cancelled by Apple but it seems that doesn’t mean you’re off the hook on a brand new two-year agreement with AT&T, so call AT&T and make sure you not hooked.