The visitor's email address should be recorded and displayed to the user in the Visitors app. The Visitors app is not useful without a human-readable visitor identifier. A JCR UUID alone doesn't help me find the visitor's personal data.

User story:

When a visitor calls me on the phone and asks what personal information the site has collected about her, I want to find the data based on her email address, so that I can give her an accurate answer or process (export, delete) the personal data further.

Acceptance criteria:

• The Visitors app records and displays the visitor's email address.
• I can search the Visitors app for an email address. 
• I can find all visitor records that share the same email address.
  • Example: Several visitors filled a form using the same shared corporate address such as info@magnolia-cms.com