I can hear the pitter patter of Apple fans racing to the store!
Update: Looks like Apple has discontinued the 4GB (see pic above). I’ve read that the AT&T stores are selling them for $299. You can also pick them up at Apple.com
Update 2: I wasn’t gonna post this but just in case…You can now get $100 back from Apple if you promise to remain a customer (wink). You’re also covered by Apple’s 14 day price protection so just Segway into your local Apple store and you’ll get $200 cash. Last but not least, if you bought the iPhone on a credit card with price protection give them a ring and see what they can do. Amex is honoring them according to Gizmodo.
Confirmed on Reuters