Media loves these guys. There is a small library worth of literature written about them; Plague of the Dead, Monster Island and World War Z just to name a few. Movies first introduced them in their modern incarnation with Night of the Living Dead back in 1968, but the big breakout surge in popularity came with the arrival of 28 Days Later. In the table top market there are board games - Mall of Horror, pen and paper RPGs - All Flesh Must Be Eaten, and card games - Zombies!!! Truth be told though this particular brand of undead is most prevalent in video games.
That's not to say they're a recent addition. Zombies have been in video games for a long time, but they have seen a major upsurge. From the indie titles such as Last Stand and Plants vs. Zombies to big budget productions like Resident Evil and Dead Rising there is a wide range of genres in which these guys hold center stage. You can find them online with Left 4 Dead and in educational software such as The Typing of the Dead. It gets worse though...in recent years zombies are starting to turn up in games they don't seem to belong in. Call of Duty, Red Dead Redemption and even the remake of Choplifter have these shambling menaces in them.
Its almost as if they were rising, spreading, infecting and devouring video games. For awhile now there has been an outcry on the internet to get rid of these things. But it hasn't impeded their proliferation. One wonders if and when a time will come in which a game or piece of DLC not featuring zombies is the exception. At the very least the presence of zombies in video games has become an epidemic. A real zombie apocalypse may never happen, but for the video industry it may very well bring about a digital entertainment end of the world crisis.