du and tar: --exclude-from option

It appears that du and tar use a different pattern language for their
--exclude-from option. I was trying to predict the size of a backup that
would be performed with tar, and came across a discrepency.

df reports that I'm using 2882M.
tar --exclude-from says that the backup is 2722M.
du with my tar-friendly exclude from reports that I'm using 2942M.
du without any exclude file reports that I'm using exactly: 2942M.

The options have the same name, and both commands hail from gnu.org, so
shouldn't they cooperate?

Linux 2.4.18, ext3, Debian Unstable, fileutils 4.1, tar 1.13.25. My exclude
file is attached.

-- 
Jacob Elder
http://www.lucidpark.net/

./.journal
./cdrom/*
./dev/gpmctl
./dev/log
./floppy/*
./initrd/*
./lost+found
./mnt/*
./proc/*
./tmp/*
./var/cache/apt/archives/*
./var/run/*
./var/spool/postfix/private/*
./var/spool/postfix/public/*