What are the real world uses of Mahout for other applications? Is Mahout provide independent components to be used by other projects for specific needs. Say for example if a particular feature or algorithm of it required by an application, then can it be used separately?
Real-world use cases include anything you can imagine involving clustering, classification or collaborative filtering. You might cluster people in your customer database to discover demographics of users that act alike. You might use classification to detect spam. You might use collaborative filtering to recommend products to users.
A lot of the project provides Hadoop jobs. They are intended to be stand-alone processes in their own right. You can certainly integrate the Hadoop jobs into your system, and reuse any of the code too. In that sense it's somewhere between a product and a library.