<p>Now that everyone is talking about MVC, I notice that the business rules are not being addressed. In the old days of the 3-tier architecture, The business rules were in the middle layer. Where do they fall in the new MVC?</p>

A quote from a Wikipedia
Article
:
MVC is often seen in web applications, where the view is the actual HTML page, and the controller is the code that gathers dynamic data and generates the content within the HTML. Finally, the
model
is represented by the actual content, usually stored in a database or in XML nodes,
and the business rules
that transform that content based on user actions.