Failing to figure out how to send an email to an individual when they sign up may be a problem. In the case of validation I tend to look at it as "What is the

Failing to figure out how to send an email to an individual when they sign up may be a problem. In the case of validation I tend to look at it as "What is the minimum I can check for to ensure that I can get the data that I need out of this form?" Too much and it becomes arduous to sign up, too little and the app ends up trying to send an order confirmation to "Matt Swanson" instead of "matt@mdswanson.com"