<p>Should the model just be data structures?  Where do the services (data access, business logic) sit in MVC?</p>

<p>Lets assume I have a view that shows a list of customer orders.  I have a controller class that handles the clicks on the view controls (buttons, etc).</p>

<p>Should the controller kick off the data access code? Think button click, reload order query. Or should this go through the model layer at all?</p>

<p>Any example code would be great!</p>

The View would relay what should happen on a click in the UI to the Control layer, which would contain ALL business logic, and would in turn call the Model layer which would only make database calls. Only the model layer should be making database calls, or you will defeat the purpose of the MVC design pattern.
Think about it this way. Let's say you change your database. You would want to limit the amount of code change required, and keep all those changes together without affecting other pieces of your application. So by keeping all data access in the Model layer, even the simple calls, you limit any changes required to the Model layer. If you were to bypass the Model layer for any reason, you would now have to extend any changes needed to any code that knows about the database, making such maintenance more complex than it should be.