Microsoft announced officially that on October 31, 2009, MSN Encarta Web sites worldwide will be discontinued, with the exception of Encarta Japan, which will be discontinued on December 31, 2009. Additionally, Microsoft will cease to sell Microsoft Student and Encarta Premium software products worldwide by June 2009.
According to Microsoft, the reason behind this decision is that "the category of traditional encyclopedias and reference material has changed. People today seek and consume information in considerably different ways than in years past. As part of Microsoft's goal to deliver the most effective and engaging resources for today's consumer, it has made the decision to exit the Encarta business."
It is hard not speculate whether Wikipedia's success has something to do with Microsoft's decision.