The site I used previously let you follow a select number (I think it was 10-20) of your friends and you would be notified when they started watching, dropped or completed a title. You could also see their reviews etc and it was my single most used feature of the site.
When I joined mdl, first thing I did after I tried to duplicate my list here, was to find some people I thought would have similar tastes in dramas as I had. And sadly realized I had no way to see if they recently started, completed or dropped a drama.
I'd like to see all that and what my friends rated dramas, their reviews before others, etc.