Duplicate name leads not showing up in the "Possible Duplicates" smart list

Issue Description
Leads with the same first and last name are not showing up in the Possible Duplicates list.

Issue Resolution
For leads to be in Possible Duplicates, they need to have the same email address which is the unique identifier in Marketo.  This is the only matching that Marketo does. If the first and last name are the same and one is missing the email address or has a different email address, Marketo will not recognize this as a duplicate.