Are pg_xlog/* fiels necessary for PITR?

Hi, I'm backing up the entire server directory from time to time.
pg_xlog/ directory containing WAL files is pretty heavy
(wal_level=archive). Can I exclude it from the regular tar archive?

#!/bin/sh

renice 20 $$ 2>/dev/null
pgsql -U pgsql -q -c "CHECKPOINT" postgres # speed up pg_start_backup()
pgsql -U pgsql -q -c "select pg_start_backup('sol')" postgres
tar -cjf - /db 2>/dev/null | ssh -q -i ~pgsql/.ssh/id_rsa -p 2022 -c
blowfish dbarchive(at)10(dot)0(dot)0(dot)1 'cat > db.tbz'
pgsql -U pgsql -q -c "select pg_stop_backup()" postgres
sleep 60 #wait for new WAL backups to appear
echo 'ssh -q dbarchive(at)10(dot)0(dot)0(dot)1 ./post-backup.sh' | su -m pgsql

I want to change tar invocation to be: tar -cjf --exclude 'db/pg_xlog/*' ...

Will there be enough data in case of recovery? (May God forbid... )))