Recently sandboxing have created quite a buzz due to Chrome OS. But one thing I will like to point out is that it is nothing new but is quite old. For those not knowing it : It is a technique when you run a programs on a specified amount of resources which it can never cross.
It is what is done when you run chroot on linux. You can't implement many of thing you can do normally. In java also your applets run on sandbox.

Now there's a utility also in linux ( gentoo) for testing out your whether applications can run on it without causing any harm. Your SELINUX is too a type of sandboxing. In python too it is available.
With the help of sandboxing a OS like chrome can make it too difficult for a cracker to compromise as he can't run a Trojan, virus or any other thing outside the sandbox. So he will not be able to gain the privileges needed to make you zombie.
But still it is quite over hype as it is possible to exploit the holes in OS and compromise it but still it seems script kiddies days are numbered.