[balinor]

IMHO, this is not something you should do. In order for it to work, you need to make the e-mail address a unique value - meaning you can't use it more than once. This prohibits customers who do NOT want to register from ordering more than once - and a significant amount of the general public doesn't like to create an account when they purchase from a store. While I agree that e-mail as the username is a good idea, it needs to be done a lot more thoroughly than it was in that thread.