Is Python good enough for big applications?
Python is ideal for web development. It's light, easy, and excels at gluing other bits together, and working with high level interfaces. If and when I do "web" development, I wouldn't use anything else.
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It's also a superior language for scripting, small cross platform applications and prototyping. It only really starts to crumble when extreme performance requirements are stringent. That is, it's holding things up in a big way. I also find it's difficult to refactor (a property of dynamic typing), and to utilize platform specific bindings. These things can be worked around (quite easily, due to Python's C implementation, and numerous modules for this purpose), just as in most other good languages.
Python is the best high level language, the only language it can't replace is C.
From the moment I have faced Python, the only thing I can say for it is "It is awesome". I am using Django framework and I am amazed by how quick things happen and how developer friendly this language is. But from many sides I hear that Python is a scripting language, and very useful for small things, experiments etc.
So the question is can a big and heavy loaded application be built in Python (and django)? As I mainly focus on web development, examples of such applications could be Stack Overflow, Facebook, Amazon etc.

P.S. According to many of the answers maybe I have to rephrase the question. There are several big applications working with Python (the best example is You Tube) so it can handle them but why then it is not so popular for large projects as (for example) Java, C++ and .NET?