I really enjoyed the Dreamforce 07 session on Advanced Segmentation and Reporting. Salesforce shared how they internally customize Salesforce to track email preferences and subscriptions for their Leads and Contacts using a custom object name "EmailPreferences".

I liked the simplicity of this approach so much that I'm resolute on adding this as an i-Dialogue feature in the next release to replace our newsletter subscription engine.

The Problem: Duplicate leads and contacts from multiple campaigns result in contact fatigue. Leads may want to subscribe to one newsletter but not others. Allowing leads to change their global "Email Out Out" setting prevents future contact on other campaigns.

The Solution:
1) Create an Email Preferences custom object for storing a unique email address and multipicklist of subscriptions.
2) Modify Lead and Contact with lookup reference to an EmailPreference object.
3) Create some Apex code that looks for existing Email Preferences on Lead/Contact create events.
4) Create an Email Preferences landing page. Update email template footers with link to preferences page (passing in user id or email address)

Step 3 is only available for unlimited edition, so we'll likely implement this step via the API to ensure backwards compatibility with our Pro and Enterprise Edition customers.

The Results: CAN-SPAM compliant. Customers can opt-out of individual newsletters managed in Salesforce. Ability to create target email lists by subscription type. Ensure only 1 unique email address per person (if duplicates exist, ensures only 1 email sent).