Yes, unfortunately the SQL Server SOUNDEX() function stops encoding a name when it encounters a non-alphabetic character.  So "DE LA POINTE", "DE LA SOUL", etc. will all encode to "D000".  One work-around with Soundex is to eliminate all spaces from a name before encoding with the REPLACE() function:

SELECT

SOUNDEX(REPLACE('DE LA POINTE',' ', ''))

Another option (that NARA recommends) is to eliminate common prefixes like 'DE', 'LA', 'VAN', 'CON', etc. from the name before Soundex-encoding it.  See http://www.archives.gov/publications/general-info-leaflets/55.html for more info.  Also note that the MS SOUNDEX() function does not follow the official NARA Soundex standard, and may return results that don't match up with external data sources that encode correctly.

This NYSIIS implementation ignores invalid characters (spaces, etc.) in the name and encodes until it runs out of alphabetic characters.  Also see http://www.sqlservercentral.com/columnists/mcoles/sql2000dbatoolkitpart3.asp for the update to this set.  The update includes NYSIIS, Double-Metaphone, Celko Soundex, Daitch-Mokotoff Soundex, Levenshtein Edit Distance and Jaro-Winkler Distance functions.