Yahoo has announced that the Yahoo! Publisher Network (YPN) will be closed down effective April 30, 2010. In a remarkable decision, Yahoo is suggesting that publishers move to Chitika, who have set up a customized process for YPN publishers. Yahoo says that all YPN publishers will be mailed final payments by May 31, 2010.

Yahoo set up YPN in August 2005 as a competitor to Google AdSense, but they have clearly decided that it n longer fits into the Carol Bartz strategic vision.

The curious thing about this announcement is why Yahoo is referring people to Chitika rather than to Microsoft’s adCenter and as yet there is nothing about this on the Yahoo blog. No doubt more will become clear over the next few days.