When users accept the Developer Agreement (Step 1 of app submission), we allow them to opt in to receive emails about the Marketplace. Currently there is no way for a user to opt-out once they sign up for this. When we add the profile pages, this should be added to /users/edit
User pages aren't a part of the marketplace beta, but adding this to the current /users/edit wouldn't hurt. The backend uses the same system as the rest of the subscriptions
This is no longer maintained by the subscriptions built in to AMO, it's all moved to exact target. Going to wontfix this.