Namespace importance:

http://higher-order.blogspot.com/2008/02/designing-clientserver-web-applications.html
http://jquery-howto.blogspot.com/2009/01/namespace-your-javascript-function-and.html
An example which utilizes 3 distinctly different sets of scripts from different organizations. We use Ext JS for enhancements, Google Analytics for tracking site usage and the native vBulletin scripts. You can see how all of this code from different sources has been included in the same page.

Namespacing is important for developers in order to organize their code and ensure that their code is not overwritten when loaded in the JavaScript interpreter. If another developer defines a variable with the same name your existing definition will be overwritten.

Because JavaScript is a functionally scoped language creating a function and/or variable which is not wrapped in another function will result in that variable being created in the global scope (window). To combat this, developers place their classes in Objects.
As the client-side JavaScript included in web applications gets larger and more advanced, organization of 3rd party code and your own code becomes increasingly important. Using namespaces will ensure your JavaScript code is safe from other code overwriting it in the global namespace.

Example grid pre-configured class,apply config, Register Grid , used as xtype
http://examples.extjs.eu/ (grid in border layout)