I agree with Joel's position wholeheartedly. I've read Robert Martin's book "Agile Software Development, Principles, Patterns, and Practices". Referring to the book, which demonstrates the SOLID principles, it's not that you can't do it that way and be successful, it's that a pure object oriented approach is not necessarily the best approach to building every kind of application. He says in his book regarding an example implementation of a payroll system, that we are paid to create "behaviors". I disagree. This detailed critique explains it well:
http://objectmix.com/theory-concepts/10776-critique-robert-c...