I've been playing around with What Should I Read Next?
which is interesting but not fully functional. I'm not just referring to the fact that the site doesn't yet have a critical mass of data for recommendations; that's understandable. What's annoying is that the interface has some bad design choices that I don't understand.
The site's killer app is that users can create a profile of books they have read and liked; this mass of book associations gets chewed up and spat back out as recommendations. So far the recommendations aren't very good, but that has a likelihood of improving with more users and more data. So far so good.
I have a few criticisms, which I will enumerate in list form.