pg_basebackup problem...

Hi all,

We've had a problem surface with the current pg_basebackup procedure we
were following. Now, I want to explain that this pre-dates me and I
recommended some additional flags to use when running it, specifically I
told the group to include "-X f -c fast". Here is the old version they were
invoking:

pg_basebackup -P -Ft -Z9 -D
/var/lib/pgsql/9.2/backups/<date_stamped_backup_filename>

The problem we're having, is the tarball these generated will not
successfully restore. That is, the tarball looks OK, but the resultant
database cannot be started as the pg_xlog directory is empty and postgres
says it can't locate the checkpoint segment to sanely initialize.

This really doesn't make sense to me. Shouldn't pg_basebackup capture the
contents of the pg_xlog directory without needing to use a "-X f" flag?
Otherwise, why could pg_basebackup create a "backup" that really is not
usable? I'm really just trying to determine why pg_xlog is empty , if it
really shouldn't be.
--
Jay