If you shop through Amazon rather than go to the local shop, you may still be supporting a small business -- one of the countless small businesses that sell through Amazon. Here in the UK there have never been more people running small, sometimes family, sometimes one-man (or woman) businesses. The great majority of these small businesses are selling online, whether through Amazon, eBay, Delcampe, etc or through their own website.
So what has changed is less a BIG** vs SMALL issue as INTERNET defeats HIGH STREET. This makes a big social change to communities. The general disappearance of big manufacturing plants that used to see neighbours working for the same firm, the replacement of buses by cars, the decline of churchgoing, and increasing ethnic diversity are all factors which tend towards the decline of community integration.
As a former shopkeeper from a family of shopkeepers (living in a "nation of shopkeepers") I regret the disappearance of diversified small shops and even of retail chains. But it seems to me a smaller problem than the dissolution of community based social life.
**But the unrivalled power of Amazon is something I do not feel happy about. Competition often used to arise through the geographic separation of rivals but that no longer applies. The web has killed geography.