I have an idea for additional overview that will fit into Profile section.
My Caching Friends (or whatever we will call it) statistics should show me the list of other geocachers sorted (DESC) by number of caches that we both found on the same day (same Found it / Attended date).
Additional filters can be applied as usual in other views.
Example: This statistics was created on Slovak geocaching.sk website and worked until data flow from gc.com was cut back in 2011. You can still check the outcome here: http://www.geocaching.sk/extra/kto-s-kym.php?login=Rikitan
Hope the link above works for anyone.