Can you give more details on your specific use case? Any smart list filter that allows you to specify a field attribute (such as "Data Value Changed") will allow you to pick any existing data field to filter by, and SFDC ID is one of those able to be selected.
We have contacts within SFDC more than one time, B2B and B2C. They are in SFDC twice due to our event ticket inventory management software. I need a way to 'define' which one (B2B or B2C) should recieve a campagin. As far as I aware, the only unique identifyer between the two is their SFDC ID.
Most common way I see customers do this is via SFDC Record Type or custom field that indicates the B2B/B2C category. Have a look at Record Type ID and see if that works for you. It will give you the cryptic SFDC ID, but it should do the trick.
Just as others have mentioned, being able to use the SFDC ID value enables us to specify a specific instance of a person (where email etc may be the same, based some 'legitimate duplicate' rules we have). It's been 5 years since this thread has had any attention, but it would be great to see this simple addition taken care of.
Records missing email address - remove from the Marketo database but keep in the Salesforce database.
Without the email address field as a unique identifier between the two systems, we have no unique identifier that can be used via filter or list import. This is especially difficult for large databases.
The idea has been voted for by 800 people over the course of 6 years. Is there an update that can be shared to this thread?