After the purchase offers before Microsoft and hardly rejected by those at Yahoo! At the beginning of the year, the relationships between the two companies were a bit cooled. Collaboration between Microsoft and Yahoo! For the project Yahoo! Messenger for Windows Vista, it seems that it was a failure from the beginning. The application of the application has submitted with the speed of the snail, and the interaction between users MSN/Live Messenger and Y!Messenger, remained at the level of versions 8.1 and 9 from Yahoo! Even for a version beta preview, Y! IM to make it difficult to make an operating system (2GB RAM/1.86 GHz).
On October 24, 2008, Yahoo! announce cessation of development and withdrawal y! m vista . No surprise. After closing the Mash (Social Network) project, it was predictable to be the next project closed by Yahoo!
I feel that the next project that will fall the same as mash, will be Yahoo! Messenger for Windows Vista. The project has not yet left Beta and is far from being completed (at least as far from Yahoo!). Until it is ready ym for Vista, Microsoft will launch Windows 7 (Blackcomb ~ Vienna).
In the third semester of this year, Yahoo! have dropped three times. Probably they will decrease, if they will go in this style. Each failed project means work for nothing and a lot of money thrown. The effects are felt and ... they see ...

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Sarah Bacon (Product Manager - Y! Messenger), explains on the official blog of Yahoo! Messenger, the causes that led to this decision. You can read the whole article here: Yahoo! Messenger for Vista version is no longer available.
Let me say one more ... "I feel"? :) In maximum 2 years, most of the users of Yahoo! Messenger will migrate to GTALK and Windows Live Messenger (Microsoft promises a lot). It all depends on Yahoo! Still.