It seems that the more games that come out the more demanding the hard drive space requirements. One series that holds true to this trend is Halo. Halo 4 will require “at least an 8GB USB flash drive or an Xbox 360 Hard Drive” to enjoy the games multiplayer content.
Xbox.com added that the hard drive option is “highly recommended” if you’re looking for an “optimal” experience. Microsoft, in a statement to Joystiq, added “Halo 4 will offer an optimal experience if played using a hard drive, but will deliver a visually impressive and immersive gameplay experience whether you use a hard drive or flash storage device.”
All multiplayer modes will require the additional space, specifically “the multiplayer modes the storage requirement applies to encompass all Xbox Live-enabled modes.”
It’s not entirely said why the additional space ie required though but its safe to say that the multiplayer modes will have added features that we’re not used to seeing in the Halo series. To be honest most that own a Xbox 360 already have a hard drive and those that don’t wish they did so it shouldn’t be too much of a shock.