Today Apple released a statement recalling all iPhone 3G ultracompact USB power adapters.
It seems a small percentage of the adapters have a predisposition for the metal prongs to snap off in the electrical socket, potentially having some unfortunate side effects.
The ultracompact USB adapters were only sold with the iPhone 3G in the following countries: US, Japan, Canada, Mexico, and some Latin American countries. The power adapters sold with the original iPhones are not included in the recall.
Apple did stress that if you have one of the ultracompact adapters that you should stop using it immediately.
Starting October 10, 2008 you may take your adapter to any Apple store and exchange it, or you can use this form to request that Apple ship you a new one. New adapters will have a green dot on them (pictured below) to differentiate them from the faulty line of adapters.