And setting hard limits is the best way of ensuring that your bigger problems ARE elsewhere :)

Anything you don't have a limit for will become a problem. I don't care how fast computers are, or how much memory they have, or whether you have fibre-optic broadband. If you treat the resources in question like they're infinite, you'll find out the hard way that they most definitely are not. And that's so silly, when you can just set a reasonable limit that guarantees you won't have any problems, and then... not have any problems.

Realistic limits aren't so hard to stick to if they're there, and enforced, right from the start.