What to watch?

I can easily find web sites that provide personalized recommendations for movies I might enjoy. I can also easily find web sites that recommend music to me based on my tastes. Why can't I find a single web site that will do the same for television programming? At a minimum I'd like to be able to say "I watch these twenty programs, and I've rated them all on a scale of one to five. Please recommend additional programs to me based on this data set."

Interwebs, why do you make this hard?