I think the limiting factor is the amount of computation required. When you take the number of variables (actors, directors, themes, box office gross, etc) x t

I think the limiting factor is the amount of computation required. When you take the number of variables (actors, directors, themes, box office gross, etc) x the number of values each of them have (dozens to thousands) x the number of users, that's a lot of crunching to do. Perhaps do some pre-crunching to find actors that have a correlation like that and then just check those. Apply the "Kevin Spacey index", if you will.