We've seen how to paste full-resolution photos into email using iPhone OS 3.0. The latest reported changes to firmware 3.1 will allow even more functionality by making it possible for users to paste full-resolution video directly to email.
As seen in this video, it's a simple process. Just hold down and use the copy function, then switch to email and paste. This feature is illustrated using iPhone OS 3.1 beta 3, which was just released this week.