What are some (concrete) use-cases for metaclasses?

Question

I have a friend who likes to use metaclasses, and regularly offers them as a solution.

I am of the mind that you almost never need to use metaclasses. Why? because I

Answer 1

The only legitimate use-case of a metaclass is to keep other nosy developers from touching your code. Once a nosy developer masters metaclasses and starts poking around with yours, throw in another level or two to keep them out. If that doesn't work, start using type.__new__ or perhaps some scheme using a recursive metaclass.

(written tongue in cheek, but I've seen this kind of obfuscation done. Django is a perfect example)