Should a service layer return view models for an MVC application?

Question

Say you have an ASP.NET MVC project and are using a service layer, such as in this contact manager tutorial on the asp.net site: http://www.asp.net/mvc/tutorials/iteration-

Answer 1

This has come a bit of an "it depends" where I work - we have generally had a controller consuming some service(s) - then combining returned DTO's into a 'ViewModel' that would then get passed to the client - either via JSON result, or bound in the Razor Template.

Thing is, about 80% of the time - the mapping of DTO to ViewModel has been 1-1. We are starting to move towards 'Where needed, just consume the DTO directly, but when the DTO and what we need in our client/view don't match up - then we create a ViewModel and do the mapping between objects as needed'.

Although I'm still not convinced that this is the best or right solution - as it ends up leading to some heated discussions of 'are we just adding X to the DTO to meet the needs of the view?'