Sometimes I check out the recommended videos and enjoy them. It doesn't take much genius to figure out that if I watched "Cavalcade of Nuclear Test Explosions" there's a good chance I might like "Planned Implosion Disasters," after all.
Sometimes the recommendations are somewhat mystifying, if not outright stupid (e.g. because you watched "Patrick Kane Hat Trick vs. Vancouver Canucks" we recommend "Susan Boyle--"Memory" from Cats"; WTF!?).
Sometimes, though, YouTube's recommendations are wrong in very subtle ways. Sometimes the logarithms (or whatever) are a bit too clever...
Take the example below. YouTube's 'bots believe that because I viewed Slim Harpo's "Shake Your Hips"...
...I might enjoy The Carpenters
At first glance it seems that you'd have to be from another planet to think there was any musical similarity between Slim Harpo and The Carpenters. It seems like a stupid recommendation, if you're a human being. Of course, YouTube's 'bots (or million gerbils running on exercise wheels hooked up to a million abaci or whatever) are not human. What do they know about music? Nothing! But they're pretty damned good at scouring text, and it's in text that they found the "connection" that led to the recommendation.
This one is easy, so I'm not going to tell you what the connection is, but feel free to speculate in post comments. (Glenn, Dave, and Sussah are disqualified! Damn, that's a clue!).