Cloud application development strategies — Brownfield or Greenfield?

The growth of cloud computing is multi-folds. The capability to launch the application almost anywhere in the world, the time to take the solution to the market, the richness of the services provided by the cloud vendors, and mostly the bare minimum requirement of just a laptop with internet connectivity for developers to develop the applications has lead to high rocketing rate in cloud adoption.

Among the many benefits, what would be the one single main advantage of cloud adoption?