Recommender systems are huge outside of Australia and USA such that most marketing managers now consider their optimisation as important as Search Engine Marketing (SEM). I can't believe we have totally missed the ball on this one, and nobody on the other side of planet, from Dubai to London has bothered to tell us!
Anwyays, here's the original seminal paper that Andreas Wiegend (ex Stanford, market genius and inventor of Prediction Markets and The BRIC Bank, Chief Scientist Emeritus of Amazon.com and inventor of recommender systems) directed and promoted this paper. It's based on proper West Coast Silicon Valley AI, with a quality discussion about a number of related techologies and market related effects that impact recommender systems.