It's abundantly clear, but it bears repeating. When we interact with each other on a variety of topics (movies, music, current events, history, linguistics, grammatical and orthographical mistakes) we get a picture of what sort of people our friends and acquaintances at this site are.

That, in turn, allows us to recommend books to them, not on the basis simply of what WE like, but on the basis of what we think THEY would like, knowing their character.

THAT is a very important thing. THAT, by itself, is part of what helps make sites like RAFO work.