Tell Siri to compose a message to someone. Siri will then read the message back and ask if you want to send it. Then say "edit message". Siri will now ask you for the edited message. In iOS 7 Siri would then confirm you want to send the edited message. In iOS 8 Siri now asks you who do you want to send the message to obviously forgetting the original recipient. This becomes irritating when using "hey Siri" in the car.