All businesses either large or medium are embracing the capabilities of SDN for better flexibility and consistency. Seeing this, small businesses are also getting involved in SDN.
Basically SDN architecture was targeting the large companies and infrastructures as they need more provisioning. Then this perception changed with SDN maturity and companies like Amazon, Google and Facebook got proficient with SDN. It managed Layer 3 switch infrastructure and focussed towards the software-centric view.