Is silk eco friendly?

As with all fibres, there is often a debate about how environmentally friendly they are. I found this article on the site of Beautiful Silks, my supplier for silk, talking about silk and soy silk:
http://www.beautifulsilks.com/pages/products/ecofriendly.html

http://www.etsy.com/listing/58897727/plum-nuno-felt-shawl