I went to Feedster and looked up Banned Books (does anyone detect a theme here?) and got to LibraryThing (which I see is also part of Thing #11). My first problem with LibraryThing is one of my problems with all of these "everyone can post what they like" sites; I'm really not sure that it's a meaningful resource for a professional. Novelist at least has editors who I know are employed and therefore their work is supervised.
On The Other Hand, I also know that bookstores often have a section called "Employees' Favorites" so that regulars of the bookstores can go to that section and use a similar search strategy (The "I know I like the books Jean likes" algorithm) and I also know from experience that sometimes customers know that they like books that a particular librarian likes, so they go up to her for recommendations.
LibraryThing's Book Suggester is more annoying than helpful, because it requires at least one more step for me to figure out what the book that's being suggested is about. I might have liked "The Other Rebecca" for any number of reasons, and because LibraryThing hasn't figured out how to manage tags (while Novelist has) means that I won't find it professionally useful, yet.