What is tempuri.org?

Question

Why does tempuri.org exist? Why does each XML Webservice require its own namespace, unique from any other on the web?

Answer 1

Webservices require unique namespaces so they don't confuse each others schemas and whatever with each other. A URL (domain, subdomain, subsubdomain, etc) is a clever identifier as it's "guaranteed" to be unique, and in most circumstances you've already got one.