If you are familiar with "Steam", you'll know about groups. Users can create their own groups, public or private/invite only, for all kind of interests.

Why I'd consider this useful is to invite already existing communities to simkl. On all kinds of forums you'll find people talking about which movies and shows they recommend - why not make it easier for them?

With groups they'd have to chance to connect with familiar names immediately. And you could offer tons of statistics based on the group's interests.
What have they seen most? What did they see in the last week? What are their favorite comedy flicks? etc. etc.

Anyway, I think you get the idea. It's a fast path to grow for you and for users to find their friends or like minded people.