SQL: Using NULL values vs. default values

Question

What are the pros and cons of using NULL values in SQL as opposed to default values?

Answer 1

To me, they are somewhat orthogonal.

Default values allow you to gracefully evolve your database schema (think adding columns) without having to modify client code. Plus, they save some typing, but relying on default values for this is IMO bad.

Nulls are just that: nulls. Missing value and a huge PITA when dealing with Three-Valued Logic.