One of the challenges with building an application these days is the number of dependencies that application will actually have on other applications. Ideally in order to know how that application will actually perform application developers would be able to test their application against the application it depends on running in production. The odds of that happening, however, are slim to none, especially if that other application is running as a cloud service that has to be always available to end users.
Take a look at our API directory and you will quickly note that the Google Maps API continues to reign as the most popular API used for mashups. As the API continues to gain momentum, several new utilities have emerged to improve the user experience (or UX as it has come to be known).