Why does everybody use unanchored namespace declarations (i.e. std:: not ::std::)?

Question

It seems to me that using unanchored namespaces is just asking for trouble later when someone puts in a new namespace that happens to have the same name as a root level name

Answer 1

This is so much artificial:

namespace fred {
namespace std {  // A standard fred component

class string { // Something rather unlike the ::std::string
   // ...
};

} // namespace std
} // namespace fred

This Fred would not be able to explain why he did that to the whole team.

To answer your question: people omit first "::" because it is a habit, which saves time and because it is easier to expect that when namespace is used anywhere, then such name is absolute, not relative.