>Example, Vendor record with an FK to an Address table. If we don't know the address for the vendor, we may have NULL in the FK field.
I really hate NULLs and if SQL Server have EMPTY() datetimes I wouldn't have any NULLable fields in Database. In the cases you point I will have an record the will be "I don't know" or something in the table with a valid key.
Against Stupidity the Gods themselves Contend in Vain - Johann Christoph Friedrich von Schiller
The only thing normal about database guys is their tables.
