Resumen
Recommender systems assist and augment a natural social process. In a typical recommender system people, provide recommendations as inputs, which tile system then aggregates and directs to appropriate recipients. In some cases, the primary transformation is in the aggregation; in others, the system's value lies in its ability to make good matches between recommenders and those seeking recommendations. This special section includes descriptions of five recommender systems. A sixth article analyzes incentives for provision of recommendations. Recommender systems introduce two interesting incentive problems. First, once one has established a profile of interests, it is easy to free ride by consuming evaluations provided by others. Second, if anyone can provide recommendations, content owners may generate mountains of positive recommendations for their own materials and negative recommendations for their competitors. Recommender systems also raise concerns about personal privacy.

Resumen
The article presents a vision of future computer-mediated economy. According to the author most market transactions in the future will also be mediated by specialists, most likely in the form of computerized agents. According to the author extraterrestrials would be discovered in the next 1,000 years, thus opening up the possibility of interstellar trade, probably limited to trade in information. Another possibility is new intelligent life-forms on Earth based on electronic or biological forms. The new forms may have radically different motivations. Technology has magnified the power of individuals, a small number of unbalanced individuals will be immensely powerful, threatening the existence of human life on the Earth. Bill Joy, chief scientist of Sun Microsystems Inc., has also warned about threat to human life on the Earth, due to advances in nanotechnology and small numbers of unbalanced individuals becoming more powerful