It would be nice if the 'unused' command could optionally display info about the actual files behind its cryptic keys.

I created a (very rough) bash script that simply splices in some info from git log -S'KEY' --numstat into the unused list, like so:

arand@mas:~/annex(master)$ bash ~/utv/scripts/annex-vunused 
unused . (checking for unused data...) (checking master...) (checking synced/master...) (checking origin/HEAD...) (checking seagate/master...)
Some annexed data is no longer used by any files:
NUMBER  KEY
1       SHA256E-s1073741824--49bc20df15e412a64472421e13fe86ff1c5165e18b2afccf160d4dc19fe68a14.img
                8f479a4 Sat Feb 23 16:14:12 2013 +0100 remove bigfile
                0       1       dummy_bigfile.img
                2988d18 Sat Feb 23 16:13:48 2013 +0100 dummy file
                1       0       dummy_bigfile.img
(To see where data was previously used, try: git log --stat -S'KEY')To remove unwanted data: git-annex dropunused NUMBER
ok

The script:

#!/bin/bash

pipe="$(mktemp -u)"
mkfifo "$pipe"

git annex unused  >"$pipe" || exit 1 &

while read -r line
do
    key="$(echo "$line" | sed 's/^[^-]*-\([^-]*\)-.*/\1/')"
    echo -n "$line"
    test -n "$key" && \
        echo && \
        git log --format="%h %cd %s" --numstat -S"$key" | \
            sed '/^$/d;/git-annex automatic sync/,/^ /d;s/^/\t\t/'

done < "$pipe"
rm "$pipe"

It would be nice if something like this was available as an option, since it's good way to get a quick overview of what the content is, and if it's safe to drop it.