[@Asura] ... again, 1/2 of your chakra doesn't sound like a lot, but even something as dumb as stepping on water technically costs chakra. Whenever a shinobi is doing things, he burns up chakra. And you only gain back as much as you have left when it dies. So, actually, having two clones shooting fireballs quickly depletes them and might even make them die purely because they're using up their own chakra. 

Also, pushing your limits in regards to chakra (i.e. using more than you should) has physical effects as well - you get sick, fatigued, etcetera. Also, you apparently pass out when you use too much chakra. If you use up 100% of your chakra, you die. 

I also wasn't saying it was impossible to make 4 clones. I'm just warning him that it's really stupid and nobody in their right mind would do that purely because it makes every battle where you do that a potential death situation.