In mid-to-late 2005, the Internet reached a “tipping point.” Internet end users began doing a lot more than creating and posting their own content (text, music, photos, videos) and commenting (via blogs) on each others’ content and ideas. Internet hobbyists--lead users--began to develop thousands of new applications by combining two or more Web services to create fun and useful combinations. These customer improvisations which build on other's work are referred to as “mash ups.”
What Are Mash Ups?
The term mash up came from the field of music. A musical mash up is a remix of two or more songs into a new piece of music.
A Web mash up is a new application that is created by pulling together two or more complementary Web-based applications and/or data sources; for example, mapping a database of known child-molesters onto a map. Every time a new person is added (or removed) from the child molester database, their location is automatically added or removed from the map.
Maps are popular platforms for mash ups. People have created dynamically updated maps showing traffic jams on their commute to work, crime incidents in their neighborhoods, all the public Wifi locations within a five-mile radius, new sightings of animal or plant species they care about, the locations of public bathrooms, the actual movement of buses along their routes, the impact of global warming on bird migrations. You simply combine a mapping service--like Google Earth, Yahoo! Maps or VirtualEarth--with any geo-coded data set, and you have an application that updates itself every time the data changes.