Do you prefer explicit namespaces or 'using' in C++?

Question

When using C++ namespaces, do you prefer to explicitly name them, like this:

std::cout << \"Hello, world!\\n\";

Or do you prefer

Answer 1

I always use using namespace for std & boost. Everything else I tend to use an explicit namespace unless it is used so much that it would clutter up the code.

In headers, I never use using namespace to avoid polluting the global namespace of the #including source.