I remember when that competition was released, I was working (as an undergrad) in GroupLens, which had MovieLens still around but it was getting a bit of bitrot.

It was always weird to me that GroupLens didn't spin up a team for it, but it seemed like everyone in the research group had moved on to other things and didn't want to context switch back. Someone mentioned something like "shame they didn't do this 10 years ago, a million dollars would have been nice". I think someone was doing tagging on movielens, but I don't remember the details.

I got the sense that neither Riedl nor Konstan (or any of the current grad students it seemed) wanted to pursue it (Terveen, I think, wasn't in to recommender systems at all in the first place).

I don't think the lab had any funding problems haha, so maybe that was what it came down to.

I remember my professor talking about the ensemble approach the competitors were taking in a data mining class I took. I was saddened when Netflix ended up not using it because it was too slow and expensive or something.