Of late, creating mashups have become a child's play. For few who are new to the terminology, mashups are the new ways of creating a new web application by combining/repurposing existing web applications. The most popular ones are built around the Google maps, where a real-estate information (like availability of apartments/houses in various areas within a city) provided by a realty web site can be mashed with a Google map of that city to produce a new UI that plots the availability right on the map itself.
My thought is Will they have any place in the mission critical Enterprise web applications ? (e.g. Online Banking). Am not sure whether any enterprise has ventured into mashups so far.
But this new paradigm will certainly change the way in which applications would be built in future. Typical IT project cycle is waterfall model - For a defined set of business requirements, a set of candidate technologies/solutions would be analyzed to find a better suit. But the mashup way of creating applications reverses the game. Using the existing APIs/services, what new applications can be built innovatively that will add value to the business & customers.