Users have the ability to add new constituent records from the Add a Relationship form. When adding a new individual with this form, CRM does not check for or attempt to match existing records.
We are currently evaluating this issue for a fix in a future service pack.
Steps to Duplicate
1. Open a constituent record 2. Click on Relationships (tab) > "Add individual" 3. On the "Related Individual" field click the New button. 4. Fill out the form with constituent information that should trigger a match to an existing constituent. 5. Click save and note that matching does not occur and a new record is created.