Allow the user to select from a short list of fields that would determine if a user is a duplicate.
This is CRITICAL to all of our clients as they are chiropractors. Often times, the entire family is getting care. However, the 10-year old girl has the same email/phone as her mother. The only way to allow this to happen is to Allow Duplicates. However, when we nurture them to make an appointment, we first have them complete a form (which creates a contact) and then request an appointment on a calendar (which creates ANOTHER contact). We suggest that you allow the user the option in the Company Information section to select the fields to be used in determining "duplicate" criteria. Simple check boxes for name, email, phone would do the trick.