Mashup Integration in Salesforce

During preparation for TA certification exam, I came across a word Mashup for integration a number of times. I explored about it and below is description:-

Mashups, sometimes called “composites,” are hybrid applications created by bringing together several data sources and Web services to create a new application or to add value to an existing application. Behind the scenes, mashups may require different levels of integration, depending on whether the mashed-up data is only meant to be viewed, whether it can be edited, and whether data is actually transferred between systems.

There are three types of mashup:-

1. Client Presentation Mashup - In this type of mashup the integration takes place strictly at the visual level. It makes possible to view data from two or more applications in a browser, without actually moving data between the applications. Example - Google Maps.
2. Client Service Mashup - As mashups evolve, they are becoming more complex and sophisticated. Client services mashups, for example, may call Web services or consume Web sites and feeds, or invoke the Salesforce API from the browser to perform a step in a business process. Such mashups can be used to streamline multi-step business processes such as order management, return material authorization, or integration with eBay auctions and Google Adwords advertising campaigns.
3. External Service Mashup - Another type of mashups is external services mashups, which treat Salesforce data as a client, using exposed Salesforce data and mashing it with data in an external system. An example of an external services mashup is an enterprise portal that displays Salesforce as one of many presentation portlets.