Componentization is achieved not only through an ECL, but different parts of the Business Processing Framework can be componentized as well. This enables implementation of specific entity-driven or process-driven functionality in one place.
For example, both the desktop store clerk application and the e-commerce web site may require the use of a Customer class with a (overloaded) Search function that enables the applications to retrieve a customer by a combination first name, last name, email, member number, Date Of Birth, phone number or even item last purchased. By implementing the Customer Class in a Business Class Library (BCL), we can enable Developer A and Developer B working on the same use case in multiple applications to share one implementation. Of course, this would also mean that when Impact analysis is done on the BCL, changes might need to be propagated to both applications. But that cost has almost always proven to be lower than the cost of maintaining redundant implementations.