squashfs filesystems require explicitly specifying the filesystem type when mounting with mount as libblkid doesn't identify them.
http://marc.info/?l=linux-ext4&m=119073995431827&w=2
Committed in e2fsprogs-1.40.2-8 (though patch not yet merged upstream)
Urgh... doesn't work on big endian boxes. Sorry, will fix that up.
Annnnd fixed (for BE too) now...