Hello itsautumn, glad it's not just me. It's a conflict really because I am shallow enough to admit that 'stuff' does sometimes make me happy. I love clothes and feel as though an interest in fashion is sometimes considered a pretty trivial hobby compared, say, to an interest in football. Which could in fact be equally trivial and expensive (although perhaps not generally the same cost to the environment).
But I don't want to be constantly wanting more stuff and that's what these Instamums do to me. I've decided to use pinterest for specific outfit inspiration and so that I use more of my existing wardrobe. That doesn't mean that I will never go shopping again, just that I hope to do so in a slightly more mindful way.
I do agree with the sustainability of the business model. It will be interesting to see.