Interspire ecommerce

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I just got a call today from someone building an ecommerce site on a platform called interspire.  It seems that there are a million SaaS ecommerce platforms out there from Prostores to Shopify to Big Commerce to Volusion.

How do they differntiate themselves?

Then you have the open source products like OS Commerce and Magento.

What is the future of ecommerce?