While cheating may not be a problem in a noncompetitive sandbox environment, griefing is. Consider a dumb client that fakes logging in to the game server and se

While cheating may not be a problem in a noncompetitive sandbox environment, griefing is. Consider a dumb client that fakes logging in to the game server and sends thousands of explosions to a player's screen at once, or drops hundreds of jets or explosive barrels everywhere instantaneously. There is practically no limit to sending these hand crafted packets in comparison to how fast the GPU will be able to render the resulting actions. So now, you have a massive DoS problem on your hands. Ideally nobody will do this, but my point is lots of problems can come up when you trust the client.