When a constituent registers through a NXT Event form, if they happen to enter an address that is not in our records, the system adds and defaults that address to the preferred address. We would like to be able to review any new addresses prior to making them preferred. If the constituent happens to mistype their address, the system will still add it as a new address and make it preferred; effectively giving the constituent an invalid address or an address that is not theirs.
We have just shipped a new setting under Tools-->Forms Settings that allows you to select whether you'd like new addresses added to existing constituent to be marked as primary or not. This will be outlined in next Tuesday's What's New!