The launch of The War Z was a bit of a travesty to be honest. The Steam page promised feature that were nowhere to be found in the buggy alpha-esque release. Steam removed the game for a time, calling it "premature" as a result of some of the claims made on the product page (100-400 km of map space, 100 players per server).
Now the game is back on Steam, with some of the more outrageously false claims removed from the product page. However, reports are that not much has changed in the game itself - so don't expect much from the game.