What role does scalability play in system design?

Let's talk about what scalability is not. Scalability does not mean that you can build a system for 10 users and expect it to grow to support 1,000. It does not mean paying for a system that could support 1,000 users, though you only have 10. Of course, this system will "scale" well. Scalability must define an environment that was built appropriately for your environment with growth needs anticipated as part of the order. Someone did not do their homework correctly if everything has changed 500% within a year's timeframe. Oftentimes instead of blaming the system's scalability, the planning folks really should get some of that blame.