What was formerly The War Z website now redirects to infestationmmo.com, indicating the name of this zombie game has been changed to Infestation: Survivor Stories (thanks IGN). The game has had controversy since launch, some of which is centered on the old name, which is easily confused with Day Z, Bohemia Interactive's Arma II zombie modification that's in development as a standalone game. The previous title is also quite similar to World War Z, the apocalyptic horror novel that's soon to be a major motion picture starring Brad Pitt, so there are two candidates for the root trademark issue mentioned in their explanation:

Effective today, The War Z has changed its name to Infestation: Survivor Stories. This change has come about primarily as a result of some confusion and trademark issues with a similarly titled property. While we were reluctant to rename the game so long after launch, especially with nearly 1 million registered players, it was ultimately decided to be in the best interest of our existing community as well as future players in order to eliminate confusion. Please rest assured that this will in NO WAY affect you as players. The only difference you will see is the change in logo and website. There will be no interruption of service or change in content.