The algorithm that the nerds over at Netflix have come up with for suggesting movies based on previously watched titles isn't perfect, but I feel like it generally makes some solid suggestions. Every now and then it'll throw me something completely out of left field, but hey, I really enjoyed Fried Green Tomatoes and if I had to watch Mega Shark vs. Crocosaurus to get to it, then so be it.
When Netflix does screw up though, man, does it ever get weird. Redditor thwmike's Netflix had a bug in it the other night and offered up some truly bizarre suggestions. (Tip: you will be deeply disapointed and may feel like crying in the fetal position if you make the mistake of watching Human Centipede under the belief that it's a goofy comedy.)