What other services could companies test internally before launching publicly?

Some other examples of companies that have successfully implemented the principle of starting slow with a big idea include Google and Facebook. Google started as a simple search engine and gradually added features like Gmail, Google Maps, and Google Drive. Facebook started as a social network for college students and gradually expanded to include other demographics and features like Marketplace and Facebook Watch.

Some strategies for ensuring that a big idea is both scalable and sustainable include starting slow, testing different features, and understanding what customers want before asking them to pay upfront. It's also beneficial to start with an internal infrastructure that can be privately tested before offering it as a service to the world.