Backward compatibility is an understandable concern, but since "DEFAULT" is one of the 124 official SQLite keywords, you would expect it not to be used for user-defined objects or else properly quoted. http://www.sqlite.org/lang_keywords.html
Additionally, adding the capability of using a "DEFAULT" literal-value satisfies the WWPD criteria. http://www.postgresql.org/docs/9.4/static/sql-insert.html
