Applications used to be monolithic, end-to-end do it all systems. Developing these mamooths often failed and still continues to fail today. Enter the idea of software ecosystems. For instance, Jan Bosch wrote about the concept in this article from 2009.
Software systems are increasingly not developed any more. They are composed. The trick is to make a minimal effort using existing components and nodes and create the business logic that ties it all together. Mashable.com is an excellent example of the power of composition.
