Blame Brad Pitt.
PC survival MMO The War Z has been renamed to Infestation: Survivor Stories. "This change has come about primarily as a result of some confusion and trademark issues with a similarly titled property," Hammerpoint Interactive's community manager wrote on the game's forum page. War Z's official Facebook and Twitter pages have been deleted.
World War Z, the film based on Max Brooks' book, is likely the subject of the trademark dispute. Hammerpoint emphasizes this will not affect players, and is purely a cosmetic adjustment to the website and title screen. Unfortunately, the game still isn't very good. You can see IGN playing the game below.