This one threw us for a loop; according to Xbox.com, Halo 4's multiplayer component will require 8GB of free hard drive space internally or via a USB flash drive.
This is just for multiplayer. We have personally not heard of a multiplayer component being so big, but Halo 4's multiplayer does offer a lot of bang for your buck. Between the new game modes, the fact that multiplayer action takes place on a UNSC ship, cooperative game modes and the Spartan Ops episodic missions, Halo 4 multiplayer is going to be the deepest multiplayer offering in any Halo game to date.
We are personally wondering if this is simply an opportunity for Microsoft to start marketing peripherals and Xbox 360 bundles in advance of the game's release this Fall, or whether you truly need the full 8GB of free space. We'll see!