Recent approaches to recommendation engines, like the genetics-inspired Pandora and social tagging pioneered by del.icio.us, are intriguing. These approaches hold the promise to provide instant gratification, without asking the user to reveal her preferences and past history. Regardless of how things unfold in the future, Amazon, Pandora and del.icio.us are examples of extraordinary recommendation technologies. We commend them and are watching in fascination for what is coming next.

Good overview of the competing approaches to making (both explicit and implicit) recommendations.