Many will watch King's IPO with Zynga, the last big mobile game creator to launch an IPO, on their mind. Zynga, valued at just under $3 billion, nose-dived shortly after going public, thanks in large part to a falling out with Facebook. King, which has almost twice as many users, is believed by many to be Zynga's heir apparent. A successful IPO will mean convincing investors that King is not fated to follow the same course as Zynga.