Upon further research, I found this tidbit:

"This is not true for all database implementations. In an Oracle RDBMS for example NULL and the empty string are considered the same thing and therefore 'Fish ' || NULL || 'Chips' results in 'Fish Chips'." (concatenation)

From wiki http://en.wikipedia.org/wiki/Null_(SQL) (yeah, I know, it's wiki)

So our assumptions about NULL may not be completely correct? If this behavior has existed in SQL and Oracle for years, we were just unaware of the inconsistency?

Always something to learn...