New York Times reporters Matt Richtel and Eric Taub phrase it nicely:

HD DVD, the beloved format of Toshiba and three Hollywood studios, died Friday after a brief illness.
The cause of death was determined to be the decision by Wal-Mart to stock only high-definition DVDs and players using the Blu-ray format.
There are no funeral plans, but retailers and industry analysts are already writing the obituary for HD DVD.
The announcement by Wal-Mart Stores, the nation’s largest retailer of DVDs, that it would stop selling the discs and machines in June when supplies are depleted comes after decisions this week by Best Buy, the largest electronics retailer, to promote Blu-ray as its preferred format and Netflix, the DVD-rental service, to stock only Blu-ray movies, phasing out HD DVD by the end of this year.
Last year, Target, one of the top sellers of electronics, discontinued selling HD DVD players in its stores, but continued to sell them online.
“The fat lady has sung,” said Rob Enderle, a technology industry analyst in Silicon Valley. “Wal-Mart is the biggest player in the DVD market. If it says HD DVD is done, you can take that as a fact.” ... [ Read the full story ]