The Price of War
A big part of Killzone: Mercenary revolves around buying new equipment that provides options for customizing your loadouts for both single-player and multiplayer. Naturally with the purchases affecting both halves of the game, the bankroll you use to buy new weapons and gear is universal. The money you earn and the purchases you make will be available to you regardless of which mode you’re playing in.
The problem with this is that the progression of purchases can be thrown completely out of whack for the campaign mode if you choose to start the game in multiplayer. Entering the online arena and earning yourself fat stacks of cash will mean you’ll be able to start the single-player levels with more weapon options available than had otherwise been intended, somewhat breaking the flow of the game.
When I brought up this issue to the developers on-site, they assured me this wouldn’t be a problem because all of the weapons are relatively equal in power and merely have functional differences (akin to comparing a shotgun and a rifle). The question then remains, why would players bother purchasing anything beyond the basics, or the bare minimum to suit their favourite playstyle? This is definitely a more speculative problem than factual at the moment, but it’s quite possible that a good deal of the progression in the game will feel worthless once you’ve achieved your first solid loadout, deflating the drive to earn anything else beyond that point.