With Netflix the problem is that a family shares one account, so a family's individuals' differing tastes messes up the ratings predictor and recommendations. Netflix supports separate profiles under one account that you can set up, but it is fairly useless because the primary account is the only one that can do streaming and you need at least two discs for the other profile to be worth anything. Still, once I set up a separate profile and rated movies how I liked them rather than some being rated by me and some by Jennie, I found that the rating system on my profile did align pretty well with my tastes. The real problem was that I'd have to constantly be logging out of my profile and into Jennie's to actually do anything.
Personally, I find that Amazon's recommendations are far worse. I think maybe if I started actually using my wishlist and put things that I actually want but would probably not buy from Amazon that it would help. Stuff like TVs and home theater receivers. Instead of "Hey you bought some games, movies, books, and batteries from us, that must be all you like. Let me show you an infinite number of variations of these things you already own." I've spent hours in the past on Amazon's site in the "Fix your recommendations" setting, but it really doesn't do much good. Sure, it gets rid of things I do not care about, but only because I marked those specific things "Not interested". The biggest help would be if they could mark products as extremely similar and not recommend them if you already own one of the similar products. I already have the StarCraft: Battlechest. I do not need or want StarCraft or StarCraft: Brood War. At the same time, I don't like to mark stuff like that as "Not interested" because I love the original StarCraft. I don't want them to get the idea that I wasn't a fan or something. So in my recommendations that stuff sits.
