Post date: Apr 7, 2015 10:38:26 AM
MovieLens is one a great project in which a startup that folded ended up giving their customer base to a bunch of academics, if I understand the history correctly. The academics have very fruitfully continued to run the project with ongoing generation of data, and lots of research into how to get communities to participate as well as algorithms for recommendation. They have just announced the release of new data sets including a 20M rating dataset with tags, and new non-archival datasets of recent data. For all the info, see