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Posted by AnthonyZwi on 17 Oct 2010 at 07:23 GMT

If you have accessed this article - please comment upon it and rate it. This provides valuable feedback and encourages further debate. As the authors, we value hearing from readers and learning of your own insights, critiques and observations. No doubt other readers too will benefit from your observations and comments.

Competing interests declared: I am a co-author of this article.