Email confirmation on registration to avoid typo?

I'm not sure if there is already a way to do this, or if I ought to add this to the feature requests. About 50% of the new user trouble tickets i get are from people who don't get an acitvation email because they mistyped their email address. I would really like to have an additional confirmation field on registration where they have to type in their email again and validate it against the first field that it matches. I don't see a way to write custom validation code on fields, but wanted to check before I added this to feature requests.