Now, Amazon has this feature where you can check "why" I'm recommended this paticular thing. It's a pattern-matching database, of course, and I'm still not sure about the internal mechanisms (I suspect it's just a simple list comparison, as opposed to a chaining expert system or neural net). So when I check some of these movies, they show up because i've rated "Twelve O'Clock High" highly.
These days virtually the only things I buy via Amazon are baby books and gear. That's all I can afford with an infant-laden book budget. I'll buy a gift for somebody's birthday here and there as well. I do, however, a lot of browsing, particularly for books where you can 'peak inside', and I'm assuming Amazon's databrain also keeps track of that someplace. Those don't show up in the 'why was I recommended' list with great regularity, but they're there.
So why did Amazon's databrain conclude I'm a big fan of submarine movies? I checked a few more of the movies, and I was recommended a bunch of them because I bought...baby books. Somewhere out there, one or two submarine-obsessed Amazon customers -- maybe a Submariner at home buying stuff for a baby, or the onshore wife of a Submariner who has dual obsessions to manage -- is buying the same baby stuff I am.
Or maybe the Databrain just thinks I should be more interested in Submarine movies. Interesting concept; it's a specialized subgenre, and for a good reason, since it combines all sorts of close-quarters dramatic situations with deadly force and an all-male cast. The subtexts are manifold. I'll work on this for an essay sometime...