Show what shows/movies you both watched when browsing someones profile
Like on the Website MyAnimeList. When visting the history page of someone elses profile it would be cool to see a little statistics on top which shows how many shows/movies you both watched or rated the same.
Joost Lettink commented
I think it would be a good idea to add that functionality in the filters tab when browsing movies or shows. Just add a username in the filter tab and you can also fade movies/shows the other profile has seen.