/ seems to be allowed, at least on ext3 (supposedly in all, ext, ext2 & ext3 at least, likely also ext4) - just try this:
f='test/file'; echo "Test: '${f}'"
for c in touch ll rm ;do
eval "${c} '${f}'"
done
That will create "test/file", surprised me too... It will create it, show it with ls command and finally remove it with rm
You can type it on one line in bash:
$ f='test/file';for c in touch ll rm ;do eval "${c} '${f}'";done
So / seems to be (bizerrely) allowed in filenames - probably many tools can get confused with such though...