How to re-recreate bug:

Maria[test]>CREATE TABLE testdefaultnow (createdtime DATETIME DEFAULT NOW());
ERROR 1067 (42000): Invalid default value for 'createdtime'

Why we need it:

While obviously there are ways around this using triggers and/or timestamps. Currently you can only have one timestamp column per table

Maria[test]>CREATE TABLE testdefaultnow (createdtime timestamp default current_timestamp(), updatedtime timestamp default current_timestamp());
ERROR 1293 (HY000): Incorrect table definition; there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause

Ideally we'd be able to create tables that have a create time and an update time.