Wtf are they doing with the 8GB of ram?

If you have large worlds and high detail, you NEED a lot of RAM, but it doesn't make CPU and GPU faster: if its use allows to avoid level dynamic loading, it just allows to use most of the computing power available, if you need to keep a lot of or all the level loaded at high detail, youjust can't do without it.

@OP: I won't discuss the compromises chosen, but I want to say a thing, and this applies to every 8th gen console: obtaining 30 to 60fps @1080p res with high detail (or in other cases 60fps stable with lower native res and/or lower detail, but still in wordls wider and with higher detail and interactivity than last gen) with HW that is quite (or very in Wii U case) low-power consumption and quite low-price, so keeping costs and possible losses on HW reasonably under control since launch, and all this at the beginning of the gen, so most likely with dev tools, OS, system libraries and programmers' experience on the platform not at their best yet, is an achievement.

No one understands FPS apparently yet these type of posts keep popping up.

COD is 60fps a lot of the time.

Killzone is 60fps a lot of the time.

Until the actual game is out and you guys run tests, you are just trolling/ignorant if you're saying Killzone has worse fps than COD or any other game that is not locked at 60.

From what I heard, and this was months ago that it was said, Guerrilla Games didn't have devkits with the 8GB of RAM. They were using devkits that had only 4GB. It is not surprising that the game is not 100% optimized to run on the PS4. They started work on this game years ago with only an idea as to what the console would have and originally Sony had only planned for half the RAM it has now. The specs were likely in constant flux as Sony tried to figure out the best specs for the most affordable price that wouldn't see them losing tons of money like last time. Even when they had most of the details sorted they were still not completely certain how the RAM was going to be allocated. So Guerrilla Games, for almost the entirety of Shadow Fall's development, was developing it with lower specs. In addition, as was already pointed out, the RAM alone is not the sole factor for how well the game runs. How much it requires of the CPU and GPU plays a big role as well.