Intro to Recommender systems - are they used anywhere?

Hello All, happy to see you back. In this post I want to cover a question: "I have not seen it, it is used anywhere?", if somebody might have that.

Simple answer would be yes, everywhere :) but let's dwell on it a little bit. I usually get a reaction from non-technical people "yeah recommendations are all those adds that pop around the place with offers for the stuff I was recently looking or searching for". That is certainly some recommender system powering those but quite heavy usage of recommender systems are also elsewhere in online services, such as online stores, online music or video sites, social networks, and others. Here are some of the players who heavily utilizes a RS: Netflix, Amazon, YouTube, Google Now, Spotify. Netflix case-study in the Recommender system handbook chapter 11.2 contains more details on this and other examples of places using recommender systems.

Netflix is a video streaming company and they say that about 80% of all viewership comes from what they recommended to users not what a user would actively search for. Their whole home page is produced by a RS speaking of which rows comes on the landing page, what is their order or what is an order of movies within a row. Even such a thing as a thumbnail of the movie is chosen by a recommender system. Netflix even values their RS at a price of $1 billion per year (link). Amazon, an online store, is very heavy on recommending right items to right audience in right spots all around their pages. I don't know it for sure neither have worked for Amazon but I believe it is pretty close when I say that most of the landing Amazon page would be put together with the help from a recommender system. The items on FB feed are picked by a recommender system. And there would be much more examples...

If you were doubting if RS were used anywhere nowadays, now you can see they are and with more and more data they will be more and more important.

Other references:
https://www.cs.umd.edu/~samir/498/Amazon-Recommendations.pdf Description of Amazon's recommender system
https://code.facebook.com/posts/861999383875667/recommending-items-to-more-than-a-billion-people/ Scaling RS at Facebook
http://hpac.rwth-aachen.de/teaching/sem-mus-16/presentations/Pruefer.pdf Spotify's slides about their RS