Usable forms for an international audience

Christina pointed to this evolt article on creating usable forms.

There is obviously a growing interest in providing services to an international market. Whether you are a North American company wanting to sell overseas, or within Australia or Europe and wanting to service a massive US market, you absolutely have to consider the differences in information likely to be provided by your users. Without doubt, validation can be an impediment to users. It is critical that you do not leap into designing a form without prior thought: how can you create a form that is usable by your local or primary audience? Additionally, how can you create a form that is usable by an international or secondary audience?